#include<iostream>
#include<algorithm>
using namespace std;
int main(){
	int n,a[105],ans=0;
	cin >> n;
	for(int i=0;i<n;i++)cin >> a[i];
	sort(a,a+n);
	for(int i=1;i<n;i+=2)ans+=a[i]-a[i-1];
	cout << ans << endl;
	return 0;
}

#include <algorithm>
#include <iostream>
#include <vector>

size_t solve(std::vector<size_t>& a)
{
	const size_t n = a.size();

	std::sort(a.begin(), a.end());

	size_t count = 0;
	for (size_t i = 0; i < n; i += 2) {
		count += a[i+1] - a[i];
	}
	return count;
}

int main()
{
	size_t n;
	std::cin >> n;

	std::vector<size_t> a(n);
	for (size_t i = 0; i < n; ++i)
		std::cin >> a[i];

	std::cout << solve(a) << '\n';

	return 0;
}

#include <algorithm>
#include <iostream>
#include <iterator>
#include <vector>

void answer(unsigned v)
{
    std::cout << v << '\n';
}

void solve(std::vector<unsigned>& a)
{
    const size_t n = a.size();

    std::sort(a.begin(), a.end());

    unsigned count = 0;
    for (size_t i = 0; i < n; i += 2)
        count += a[i+1] - a[i];

    answer(count);
}

int main()
{
    size_t n;
    std::cin >> n;

    std::vector<unsigned> a(n);
    std::copy_n(std::istream_iterator<unsigned>(std::cin), std::size(a), std::begin(a));

    solve(a);

    return 0;
}

#include<bits/stdc++.h>
using namespace std;
const int maxn=100+5;
int n,a[maxn];
int read() {
    int x=0,f=1;
    char ch=getchar();
    while(ch>'9'||ch<'0'){if(ch=='-')f=-1;ch=getchar();}
    while(ch<='9'&&ch>='0'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}
int main() {
	cin>>n;
	for(int i=1;i<=n;i++)
		cin>>a[i];
	sort(a+1,a+1+n);
	int ans=0;
	for(int i=1;i<=n;i+=2){
		ans+=abs(a[i]-a[i+1]);
	}
	printf("%d\n",ans);
    return 0;
}

#include <bits/stdc++.h>
#define ll long long
#define str string
using namespace std;
int main(){
	ll n,cnt=0;
	cin>>n;
	ll a[n];
	for(ll i=0;i<n;i++){
		cin>>a[i];
	}
	sort(a,a+n);
	for(ll i=0;i<n-1;i+=2){
		cnt+=a[i+1]-a[i];
 }
 	cout<<cnt;
}

#include<bits/stdc++.h>
using namespace std ;

int main(){
	int n , pri = 0 ;
	cin >> n ;
	int arr[n] ;
	for( int i = 0 ; i < n ; i++ ){
		cin >> arr[i] ;
	}
	sort( arr , arr + n ) ;
	for( int i = 1 ; i < n ; i += 2 ){
		pri += abs( arr[i] - arr[i-1] ) ;
	}
	cout << pri ;
}

// start : 77 ; 17:30
//https://atcoder.jp/contests/agc005/tasks
//120

#pragma GCC optimize(2)
#include<bits/stdc++.h>
using namespace std;
const int man = 2e5+10;
#define IOS ios::sync_with_stdio(0)
#define ull unsigned ll
#define uint unsigned
#define pai pair<int,int>
#define pal pair<ll,ll>
#define IT iterator
#define pb push_back
#define fi first
#define se second
#define For(i,j,k) for (int i=(int)(j);i<=(int)(k);++i)
#define Rep(i,j,k) for (int i=(int)(j);i>=(int)(k);--i)
#define endl '\n'
#define ll long long
const ll mod = 1e9+7;

signed main() {
	#ifndef ONLINE_JUDGE
		//freopen("in.txt", "r", stdin);
		//freopen("out.txt","w",stdout);
	#endif
	int a[110];
	int n;cin >> n;
	for(int i = 1;i <= n;++i)cin >> a[i];
	sort(a+1,a+1+n);
	int ans = 0;
	for(int i = 1;i <= n;i += 2)ans += a[i+1] - a[i];
	cout << ans<< endl;
	return 0;
}

#include<bits/stdc++.h>
using namespace std;
int main()
{
	int n,a[105],ans=0;
	cin>>n;
	for(int i=1;i<=n;i++)cin>>a[i];
	sort(a+1,a+n+1);
	for(int i=1;i<=n;i+=2)
	{
		ans+=a[i+1]-a[i];
	}
	cout<<ans<<endl;
}

#include <iostream>
using namespace std;
int main()
{
    int nofstudents,temp, x,problems =0;
    cin >> nofstudents;
    int skills [nofstudents];
    bool change;

    for(int i = 0; i<nofstudents; ++i){
        cin >> x;
        skills[i] = x;
    }
    do{
        change = false;
        for(int i = 0; i<(nofstudents-1); i++){
        if(skills[i+1] < skills[i])
        {
            temp = skills[i+1];
            skills[i+1] = skills[i];
            skills[i] = temp;
            change = true;
        }
    }
}
     while(change);
     for(int i = 0; i<nofstudents; i=i+2){
        if(skills[i]!=skills[i+1])
            problems = problems + (skills[i+1]-skills[i]);
     }
    cout << problems;
    return 0;
}

#include <iostream>
#include <algorithm>
using namespace std;

int main() {
	int n;
	cin>>n;
	int a[n];
	for(int i=0;i<n;i++){
		cin>>a[i];
	}
	int c=0;
	sort(a,a+n);
	for(int i=0;i<n;i++){
		c+=a[i+1]-a[i];

		i++;
	}
	cout<<c;

	// your code goes here
	return 0;
}

#include <iostream>
#include <algorithm>
using namespace std;
int a[100001];
int n,sum=0;
int main(){
	int i,j,k;
	cin>>n;
	for(i=1;i<=n;i++)cin>>a[i];
	sort(a+1,a+n+1);
	for(i=1;i<=n;i+=2)
	sum+=(a[i+1]-a[i]);
	cout<<sum<<endl;
	return 0;
}

#include <bits/stdc++.h>
using namespace std;

#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define endl "\n";
#define ll long long int;
#define MAX 1000000009

int main()
 {
	IOS;
	int n;
	cin >> n;
	int a[n];
	for(int i =0;i<n;i++)
	{
		cin >> a[i];
	}
	sort(a,a+n);
	int sum(0);
	for(int i = 1;i<n;i+=2)
	{
		sum+=abs(a[i]-a[i-1]);
	}
	cout << sum;
	return 0;
  }

#include <iostream>
#include <algorithm>

using namespace std;

int main()
{
    int n;
    cin >> n;
    int* arr = new int[n];

    for(int i = 0; i < n; i++)
    {
       cin >> arr[i];
    }
    sort(arr, arr + n);

    int diff = 0;

    for(int i = 0; i < n; i += 2)
    {
        diff += abs(arr[i] - arr[i+1]);
    }

    cout << diff;

    return 0;
}

#include<bits/stdc++.h>
using namespace std;
int n,a[110],num;
int main()
{
	//freopen(".in","r",stdin);
	//freopen(".out","w",stdout);
	cin>>n;
	for(int i=1;i<=n;i++) cin>>a[i];
	sort(a+1,a+n+1);
	for(int i=1;i<=n/2;i++)
	{
		num+=a[2*i]-a[2*i-1];
	}
	cout<<num;
	return 0;
}

#include<iostream>
#include<algorithm>
using namespace std;
#include<vector>

int main() {
	int n;
	cin >> n;
    vector<int> a;
    int t;
    for(int i=0;i<n;++i)
    {
        cin >> t;
        a.push_back(t);
    }
    t=0;
    sort(a.begin(),a.end());
    for(int i=0;i<n/2;++i)
        t+=a[2*i+1]-a[2*i];
    cout << t;
	return 0;
}

#include <iostream>
#include <algorithm>
using namespace std;

int main()
{
    int n=0, result=0;
    int arr[102];
    cin>>n;
    for(int i=0; i<n; i++)
    {
        cin>>arr[i];
    }
    sort(arr, arr+n);
    for(int i=n-1; i>0; i-=2)
    {
        result+=arr[i]-arr[i-1];
    }
    cout<<result;
    return 0;
}

#include <iostream>
#include <stdio.h>
#include <string.h>
#include <algorithm>

using namespace std;

int n, x[100005];
char s[100005];
int num;

int main() {
    cin >> n;
    for(int i = 0; i < n; i++) {
        cin >> x[i];
    }
    sort(x, x+n);
    for(int i = 0; i < n; i+=2) {
        num += x[i+1]-x[i];
    }
    cout << num << endl;
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
int main()
{

    int n;
    cin>>n;
    vector<int>a(n);

    for(int i=0;i<n;i++)
    {
        cin>>a[i];

    }
    sort(a.begin(),a.end());
    int sum=0;
    for(int i=0;i<n;i+=2)
    {
        sum+=a[i+1]-a[i];
    }
    cout<<sum<<endl;
    return 0;
}

#include <iostream>
#include<algorithm>

using namespace std;
int main()
{
    int n, max=0, diff;
    cin>>n;
    int a[n];
    for(int i=0; i<n; i++) cin>>a[i];

    sort(a, a+n);

    for(int i=0; i<n;i+=2){
        diff=a[i+1]-a[i];
        max+=diff;
    }
    cout<<max<<endl;
    return 0;
}

#include <bits/stdc++.h>
using namespace std;
int i,n,ans,a[105];
int main(){
cin>>n;
for(i=0;i<n;i++)
cin>>a[i];
sort(a,a+n);
for(i=0;i<n-1; i+=2)
ans+=a[i+1]-a[i];
cout<<ans<<endl;
}

#include<bits/stdc++.h>
using namespace std;
int main()
{
    ios::sync_with_stdio(false);
    int n;
    cin>>n;
    int ans=0;
    int a[n];
    for(int i=0;i<n;i++)
    {
        cin>>a[i];
    }
    sort (a,a+n);
    int v=n/2;
    for(int i=0;i<n;i++)
    {
        if(a[i]!=a[i+1] &&v>=0)
           {
               ans+=a[i+1]-a[i];
               i++;
               v--;

           }
           else

           {
             i++;
             v--;
           }

    }
    return cout<<ans<<endl,0;
}

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int main() {
    int temp=0,t,diff=0;
    vector<int> v;
    cin>>t;

    for (int i=0; i<t; i++) {
        cin>>temp;
        v.push_back(temp);

    }

    sort(v.begin(), v.end());
    for (int i=0; i<t; i=i+2) {
        diff+=v[i+1]-v[i];

    }
    cout<<diff<<endl;
    return 0;
}

#include <bits/stdc++.h>

using namespace std;

int main() {

	int n;
	cin >> n;
	vector<int> a(n);
	for (int i = 0; i < n; i++)
	{
		cin >> a[i];
	}

	sort(a.begin(), a.end());
	int sum = 0;
	for (int i = 0; i < n; i += 2) {
		sum += a[i + 1] - a[i];
	}

	cout << sum << endl;

	return 0;
}

#include<bits/stdc++.h>
#define inf 0x3f3f3f3f
#define pb push_back
#define y second
#define x first

using namespace std;
typedef long long INT;
typedef pair<int, int> pii;
template<typename T, typename U> inline void smin(T &a, const U &b) {if(a>b) a=b;}
template<typename T, typename U> inline void smax(T &a, const U &b) {if(a<b) a=b;}
typedef vector<int> VI;

#define NN 110

int a[NN];

int main() {
#ifndef	ONLINE_JUDGE
	freopen("in.in", "r", stdin);
	freopen("out.out", "w", stdout);
#endif

	int n; scanf("%d", &n);
	for(int i=0; i<n; i++) scanf("%d", a+i);
	sort(a, a+n);

	int ans=0;
	for(int i=0; i<n; i++) {
		if(i&1) ans+=a[i];
		else ans-=a[i];
	}
	printf("%d\n", ans);
}

#include<stdio.h>

int main()
{
	int n,skill[100],count=0;
	scanf("%d",&n);
	for(int q=0;q<n;q++)
	{
		scanf("%d",&skill[q]);
	}

	int temp;
	for(int q=0;q<n-1;q++)
	{
		for(int w=0;w<n-1;w++)
		{
			if(skill[w]<skill[w+1])
			{
				temp=skill[w];
				skill[w]=skill[w+1];
				skill[w+1]=temp;
			}
		}
	}

	for(int q=0;q<n;q+=2)
	{
		count=count+(skill[q]-skill[q+1]);
	}
	printf("%d",count);
}

#include<bits/stdc++.h>
using namespace std;
typedef long long INT;
int a[111];
int main(){
	int n; cin>>n;
	for(int i=1; i<=n; i++) cin>>a[i];
	sort(a+1, a+n+1);
	int ans = 0;
	for(int i=1; i<=n; i++) {
		if(i % 2) ans -= a[i];
		else ans += a[i];
	}
	cout<<ans<<endl;
}

#include<bits/stdc++.h>
using namespace std;
#define NN 110
int a[NN],b[NN];
int main(){
	int n,s=0,t;
	cin>>n;
	for(int i=1;i<=n;i++) cin>>a[i];
	sort(a+1,a+n+1);
	for(int i=1;i<n;i+=2){
		s+=abs(a[i+1]-a[i]);
	}
	printf("%d",s);
}

#include<iostream>
#include<string>
#include<cmath>
#include<algorithm>
using namespace std;
void sor(int a[], int n) {
	for (int i = 0; i < n; ++i)
		for (int j = 0; j < n - i; ++j)
			if (a[j] > a[j + 1])
				swap(a[j], a[j + 1]);
}
int main() {
	int n, a[100], ANS = 0;
	cin >> n;
	for (int i = 0; i < n; ++i)
		cin >> a[i];
	sor(a, n - 1);
	for (int i = 0; i < n; i += 2)
		ANS += a[i + 1] - a[i];
	cout << ANS;
	return 0;
}

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main()
{

	int n, key = 0;
	cin >> n;
	vector <int> vect(n);
	for (int i = 0; i < n; i++)
	{
		cin >> vect[i];
	}
	sort(vect.begin(), vect.end());
	for (int i = 0; i < n; i++)
	{
		if (i % 2 != 0)
		{
			key += vect[i] - vect[i - 1];
		}
	}
	cout << key;
	return 0;
}

#include <iostream>
using namespace std;

int main()
{
    int n,i,c=0,t;
    cin >> n;
    int a[n];
    for(i=0;i<n;i++)
        cin >> a[i];
    for(i=0;i<n-1;i++)
    {
        for(int j=i+1;j<n;j++)
        {
            if(a[j]<a[i])
            {
                t=a[j];
                a[j]=a[i];
                a[i]=t;
            }
        }
    }
    for(i=0;i<n;i=i+2)
        c+=a[i+1]-a[i];
    cout << c;
    return 0;
}

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;
int main() {
	int n;
	int t = 0;
	cin >> n;
	vector <int> v(n);
	for (int o = 0; o < n; o++)
	{
		cin >> v[o];
	}
	sort(v.begin(), v.end());
	for (int i = 1; i < n; i = i + 2) {

			if (v[i] == v[i - 1]) {}
			else { t = t + v[i] - v[i - 1]; }
		}

		cout << t;
	}

//6
//5 10 2 3 14 5

#include<bits/stdc++.h>
#define fi first
#define se second
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define rrep(i,n) for(int i = 1; i <= (n); ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
#define rng(a) a.begin(),a.end()
#define maxs(x,y) x = max(x,y)
#define mins(x,y) x = min(x,y)
#define pb push_back
#define sz(x) (int)(x).size()
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<P> vp;

int main(){
    int n;
    cin >> n;
    vector<int> a(n);
    rep(i,n) cin >> a[i];
    sort(rng(a));
    reverse(rng(a));
    int ans = 0;
    for(int i = 1;i<n;i+=2){
        ans+=a[i-1]-a[i];
    }
    cout << ans;
}

#include <iostream>
#include <algorithm>
using namespace std;

int main() {
	int n;
	cin >> n;
	int a[n+1];
	for(int i = 0; i < n; i++){
        cin >> a[i];
	}
	int sum = 0, k = 0;
	sort(a, a+n);
	for(int i = 1; i < n; i++){
        if(a[i] == a[i-1]){
            a[i] = -1;
            a[i-1] = -1;
        }
	}
	for(int i = 0; i < n; i++){
        if(a[i] != -1){
            a[k++] = a[i];
        }
	}
	n = k;
	for(int i = 0; i < n; i += 2){
        sum += a[i+1]-a[i];
	}
	cout << sum;
	return 0;
}

#include<iostream>
#include<stdio.h>
#include<vector>
using namespace std;
int main(){
	int n,i,x,res=0;
	scanf("%d",&n);
	int v[101]{};
	vector<int> a;
	for(i=0;i<n;i++){
		scanf("%d",&x);
		v[x]++;
	}
	for(i=0;i<101;i++) if(v[i]%2==1) a.push_back(i);
	for(i=0;i<a.size();i+=2) res+=(a[i+1]-a[i]);
	printf("%d\n",res);
return 0;
}

#include<iostream>
#include<algorithm>
using namespace std;

int main()
{
	int n, sum = 0;;
	cin >> n;
	int*num = new int[n];
	for (int i = 0; i < n; ++i)
		cin >> num[i];
	sort(num, num + n);
	for (int i = 0; i < n / 2; ++i)
		sum += (num[2 * i + 1] - num[2 * i]);
	cout << sum << endl;
	return 0;
}

//author:Darshik Hirapara
//DDU-Nadiad
#include<bits/stdc++.h>
using namespace std;
#define rip(a,b,c) for(a=b; a<c; a++)
int main()
{
	int t;
	cin>>t;
	int i, j, sum=0, sm_index, no[t];
	for(i=0; i<t; i++)
	{
		cin>>no[i];
		//cout<<sum;
	}
	//cout<<sum;
	rip(i, 0, t)
	{
		sm_index=i;
		rip(j, i+1, t)
		{
			if(no[j]>no[sm_index])
			{
				sm_index=j;
			}
		}
		if(sm_index>i)
		{
			no[sm_index]=no[sm_index] + no[i];
			no[i]=no[sm_index]-no[i];
			no[sm_index]=no[sm_index]-no[i];
		}
		//cout<<sum;
	}
	/*rip(i, 0, t)
	{
		cout<<no[i]<<endl;
	}*/
	rip(i, 0, t-1)
	{
		sum+=(no[i]-no[i+1]);
		i++;
	}
	cout<<sum;
	return 0;
}

#include<iostream>
#include<algorithm>
using namespace std;

bool sap(int i,int j){
	return i>j;
}

int main(){
	int n,a[101];
	while(cin>>n){
		if(n%2==0) break;
	}
	for(int i=0;i<n;i++){
		cin>>a[i];
	}
	sort(a,a+n,sap);
	int sum=0;
	for(int i=0;i<n;i+=2){
		if(a[i]!=a[i+1]){
			sum+=a[i]-a[i+1];
		}
	}
	cout<<endl<<sum;
}

#include<bits/stdc++.h>
using namespace std;

int main()
{
    int n;
    cin>>n;
    int A[n+3];
    for(int i=0; i<n; i++)
    {
        cin>>A[i];
    }

    sort(A,A+n);
    int ans=0;

    for(int i=0; i<n-1; i=i+2)
    {
        ans+=A[i+1]-A[i];
    }

    cout<<ans<<endl;

    return 0;
}

#include<iostream>
using namespace std;
int main()
{

    long long int a , i , b = 0 , j = 0 , v = 0  , x = 0;
    cin>>a;
    long long int n[a + 2];
    n[a + 1] = 0;
    for(i = 0 ; i < a; i++)
    {
        n[i] = 0;
        cin>> n[i];
    }
    for(j = 0 ; j < a; j++)
    {
        for(i = 0 ; i < a; i++)
    {
        if(n[i] > n[i + 1])
        {
            b = n[i];
            n[i] = n[i + 1];
            n[i + 1] = b;
        }
    }
    }
    for(i = 0; i < a; i += 2)
    {
        v +=  n[i + 1] - n[i];
    }
    cout<<v;
    return 0;
}

#include<bits/stdc++.h>

using namespace std;

int main() {
    int n,c=0;
    cin>>n;
    int ar[n];
    for(int i=0;i<n;i++) {
        cin>>ar[i];
    }
    sort(ar,ar+n);
    for(int i=1;i<n;i+=2) {
        c+=(ar[i]-ar[i-1]);
    }
    cout<<c;
    return 0;
}

#include <iostream>
#include <algorithm>
#include <stdio.h>
#include <stdlib.h>
#include <vector>
#include <string>
using namespace std;

int main() {
	int n, a[100];
	cin >> n;
	for (int i = 0; i < n; i++) {
		cin >> a[i];
	}
	sort(a, a + n);
	int cnt = 0;
	for (int i = n - 1; i >= 0; i-=2) {
		cnt = cnt + (a[i] - a[i - 1]);
	}
	cout << cnt << endl;
	return 0;
}

#include <bits/stdc++.h>
using namespace std;
const int N = 105;
int a[N], ans = 0;
template <class T> void cmax(T &x, T y) {x = x > y ? x : y;}
template <class T> void cmin(T &x, T y) {x = x < y ? x : y;}
template <class T> void rd(T &x) {
	char c = getchar(); int f = 1; x = 0;
	for (; !isdigit(c); c = getchar()) if (c == '-') f = -1;
	for (; isdigit(c); c = getchar()) x = x * 10 + c - '0';
	x *= f;
}
int main() {
	int i, n; rd(n);
	for (i = 1; i <= n; ++i) rd(a[i]);
	sort(a + 1, a + n + 1);
	for (i = 1; i <= n; i += 2) ans += a[i + 1] - a[i];
	cout << ans << '\n';
	return 0;
}

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<string>
#include<cmath>
using namespace std;
int n,ans,s[11111];
int main(){
	scanf("%d",&n);
	for(int i=1;i<=n;i++) scanf("%d",&s[i]);
	sort(s+1,s+1+n);
	for(int i=1;i<=n;i+=2) ans+=s[i+1]-s[i];
	printf("%d\n",ans);
}

#include<bits/stdc++.h>
using namespace std;
int a[101];
int n;
int ans;
int main(){
	cin>>n;
	for(int i=1;i<=n;++i)
		cin>>a[i];
	sort(a+1,a+n+1);
	for(int i=1;i<=n-1;i+=2){
		ans+=(a[i+1]-a[i]);
	}cout<<ans;
	return 0;
}

#include <bits/stdc++.h>
using namespace std;
int main(){
	int n;
	cin>>n;
	vector <int> habilidad;
	for(int i=0; i<n; i++){
		int temp;
		cin>>temp;
		habilidad.push_back(temp);
	}
	//formar parejas
	sort(habilidad.begin(), habilidad.end());
	int cont=0;
	for(int i=0; i<n; i+=2){
		int more=abs(habilidad[i]-habilidad[i+1]);
		cont=cont+more;
	}

	cout<<cont;
	return 0;
}

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n;
    cin>>n;
    int x[n+4];
    for(int i=0;i<n;i++)
    {
        cin>>x[i];
    }
    int m=0;
    sort(x,x+n);
    for(int i=0;i<n;i=i+2)
    {
    m+=x[i+1]-x[i];
    }
    cout<<m<<endl;
    return 0;
}

#include <bits/stdc++.h>
using namespace std;

        int n,a[100],c;
      int main ()
        {
            cin>>n;

            for ( int i=0 ; i<n ; i++ )
               cin>>a[i];

            sort(a,a+n);

            for ( int i=0 ; i<n ; i+=2 )
            {
                   if ( i==99 )
                    break;

            else   if ( (a[i]==a[i+1])  )
                    continue;
            else
                        c+=(a[i+1]-a[i]);
            }

               cout<<c<<endl;

        return 0;

        }

#include <iostream>
#include<vector>
#include<algorithm>
using namespace std;
int main() {
	// your code goes here
	int n;
	int ctr=0;
	int arr[100];
	cin>>n;
	for(int i=0;i<n;i++)
	{
	    cin>>arr[i];
	}
	sort(arr,arr+n);
	for(int j=0;j<n;)
	{
	    ctr=ctr+arr[j+1]-arr[j];
	    j=j+2;
	}
	cout<<ctr;
	return 0;
}

#include <iostream>
using namespace std;
int main()
{
	const int a = 100;
	int n, i, A[a] = {0}, nmin, j, counter=0;
	cin >> n;
	for (i = 0; i < n; i++)
		cin >> A[i];
	for (i = 0; i < n - 1; i++)
	{
		nmin = i;
		for ( j = i + 1; j < n; j++)
			if (A[j] < A[nmin] && A[j] != 0 && A[nmin] != 0)
				nmin = j;
		if (nmin != i && A[nmin] != 0 && A[nmin] != 0)
		{
			int temp;
			temp = A[i];
			A[i] = A[nmin];
			A[nmin] = temp;
		}
	}
	for (i = n - 1; i >= 1;)
	{
		counter += A[i] - A[i - 1];
		i -= 2;
	}
	cout << counter;
		return 0;
}

#include<bits/stdc++.h>
using namespace std;

int32_t main()
{
	// freopen("inf.txt", "r", stdin);
	// freopen("out.txt", "w", stdout);

	#define int long long
   	int n;
   	cin>>n;
   	vector<int> a(n);
   	for(auto &x: a) cin>>x;
   	sort(a.begin(),a.end());
   	int ans=0;
   	for(int i=0;i<n;i+=2)
   	{
   		ans+=(a[i+1]-a[i]);
   	}
   	cout<<ans;
}

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;

int main(){
	long long n;
	cin >> n;
	vector<long long> v(n);
	for(long long i = 0; i < n; ++i){
		cin >> v[i];
	}
	sort(v.begin(), v.end());
	long long res = 0;
	for(long long i = 0; i < n; i += 2){
		res += v[i + 1] - v[i];
	}
	cout << res << endl;
	return 0;
}

#include<iostream>
#include<algorithm>
using namespace std;
int main(){
    int n,sum=0;
    cin>>n;
    int a[n];
    for(int i=0;i<n;i++)
        cin>>a[i];
    sort(a,a+n);
    for(int i=0;i<n-1;i+=2){
        sum+=abs(a[i]-a[i+1]);
    }
    cout<<sum;
    return 0;
}

#include<iostream>
#include<algorithm>
using namespace std;
int main()
{
    int n;
    cin>>n;
    int a[n];
    for(int i=0;i<n;i++)
    {
        cin>>a[i];
    }

    sort(a,a+n);
    int x,sum=0;
    for(int i=0;i<n;i+=2)
    {
        x=abs(a[i]-a[i+1]);
        sum+=x;
    }

    cout<<sum;
}

/*
Problem:
	Given the array and the integer k as input
	Selecting the kth smallest element in an n-element array
QuickSelect(one-armed quicksort) Algorithm:
	Step1: Choose a pivot element from the array
	Step2: Partition the array into three subarrays containing the elements smaller than the pivot,
		   the pivot element itself, and the elements larger than the pivot.
	Step3: Recursively quickSelect the first or last subarrays.

	Partition(A[1 .. n], p)  :  return r - the idex of p in rearanged A[1 .. n] such that A[i..r-1] < A[r]=pivot <= A[r+1..n]
	QuickSelect(A[1 .. n], k):
		if n = 1
			return 1
		Choose pivot element A[p]
		r <- Partition(A[1..n], p)
		if(k > r)
			return QuickSelect(A[r+1..n], k-r)
		if(k < r)
			return QuickSelect(A[1..r], k)
		return r

----Quickselect was first described by Tony Hoare in 1961, literally on the same page where he first published quicksort

Complexity:
	Denpend on the value of pivot.
		pivot is median ("average case")						 : O(nlogn)
		2 subproblems are completely unbanlanced (worst case)    : O(n^2)
Specific problem: https://codeforces.com/problemset/problem/1092/B
*/

#include <iostream>
#include <algorithm>
#include <fstream>
using namespace std;

int Partition(int A[], int Left, int Right, int p) {
	int l = Left-1;
	swap(A[Right], A[p]);
	for(int i = Left; i < Right; i++) {
		if(A[i] < A[Right]) {
			l++;
			swap(A[i], A[l]);
		}
	}
	swap(A[Right], A[l+1]);
	return l+1;
}

int QuickSelect(int A[], int Left, int Right, int k) {
	if(Left == Right)
		return A[Left];
	int p = (Right + Left)/2;
	int r = Partition(A, Left, Right, p);
	if(k > (r - Left + 1))
		return QuickSelect(A, r+1, Right, k-(r - Left + 1));
	if(k < (r - Left + 1))
		return QuickSelect(A, Left, r-1, k);
	return A[r];
}

const int MAXN = 1e3+1;
int A[MAXN];
void Application() {
	int n;
	scanf("%d", &n);
	for(int i = 0; i < n; i++)
		scanf("%d", A+i);

	int ans = 0;
	for(int i = 0; i < n; i+=2)
		ans += (QuickSelect(A, 0, n-1, i+2) - QuickSelect(A, 0, n-1, i+1));
	printf("%d\n", ans);
}
int main() {
	int n;
	Application();
	return 0;
}

/*
Problem:
	Sort array of integer (A)
QuickSort Algorithm:
	Step1: Choose a pivot element from the array
	Step2: Partition the array into three subarrays containing the elements smaller than the pivot,
		   the pivot element itself, and the elements larger than the pivot.
	Step3: Recursively QuickSort the first and last subarrays.

	Partition(A[1 .. n], p)  :  return r - the idex of p in rearanged A[1 .. n] such that A[i..r-1] < A[r]=pivot <= A[r+1..n]
	QuickSort(A[1 .. n]):	{correct=>doNothing} 			, if n = 1
							{choose pivot element A[p]
							 r <- Partition(A[1..n], p)
							 QuickSort(A[1 .. r])			, if n > 1
							 QuiclSort(A[r+1 .. n]}

----The algorithm was discovered by Tony Hoare in 1959 and first published in 1961.

Complexity:
	Denpend on the value of pivot.
		pivot is median ("average case")						 : O(nlogn)
		2 subproblems are completely unbanlanced (worst case)    : O(n^2)
Specific problem: https://codeforces.com/problemset/problem/1092/B
*/

#include <iostream>
#include <algorithm>
#include <fstream>
using namespace std;

int Partition(int A[], int Left, int Right, int p) {
	int l = Left-1;
	swap(A[p], A[Right]);
	for(int i = Left; i < Right; i++)
		if(A[i] < A[Right]) {
			l++;
			swap(A[i], A[l]);
		}
	swap(A[Right], A[l+1]);
	return l+1;
}

void QuickSort(int A[], int Left, int Right) {
	if(Left >= Right)
		return;
	int p = Right;
	int r = Partition(A, Left, Right, p);
	QuickSort(A, Left, r-1);
	QuickSort(A, r+1, Right);
}

const int MAXN = 1e3+1;
int A[MAXN];
void Application() {
	int n;
	scanf("%d", &n);
	for(int i = 0; i < n; i++)
		scanf("%d", A+i);
	QuickSort(A, 0, n-1);
	int ans = 0;

	for(int i = 0; i < n; i+=2)
		ans += (A[i+1] - A[i]);
	printf("%d\n", ans);
}

int main(){
	Application();
	return 0;
}

#include<stdio.h>
#include<iostream>
#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n;
    cin>>n;
    int arr[n];
     int sum=0;
    for(int i=0;i<n;i++)
    {
        cin>>arr[i];
    }
    sort(arr,arr+n);
    for(int i=0;i<n;i=i+2)
    {
        sum+=arr[i+1]-arr[i];
    }
    cout<<sum;
}

#include <iostream>
#include <algorithm>
using namespace std;
int main()
{
	int n,s=0;
	cin >> n;
	int a[150];
	for (int i = 1; i <= n; i++)
		cin >> a[i];
	sort(a + 1, a + n+1);
	for (int i = 1; i <= n - 1; i += 2)
	{
		s += a[i + 1] - a[i];
	}
	cout << s << endl;
}

#include <iostream>
#include <string>
#include <string.h>
#include <algorithm>
using namespace std;
typedef _int64 ll;
int a[110];
int main()
{
	//freopen("in.txt","r",stdin);
	int n,i;
	while(cin>>n)
	{
		for( i = 0 ; i < n ; i++)
			cin>>a[i];
		sort(a,a+n);
		int ans=0;
		for( i = 1 ; i < n ; i+=2)
		{
			ans+=a[i]-a[i-1];
		}
		cout<<ans<<endl;
	}
	return 0;
}

#include<bits/stdc++.h>
using namespace std;

void swap(int *a, int*b)
{
    int tmp=*a;
    *a=*b;
    *b=tmp;
}
int partition (int arr[], int low, int high)
{
    int pivot = arr[high]; // pivot
    int i = (low - 1); // Index of smaller element

    for (int j = low; j <= high - 1; j++)
    {
        // If current element is smaller than the pivot
        if (arr[j] < pivot)
        {
            i++; // increment index of smaller element
            swap(&arr[i], &arr[j]);
        }
    }
    swap(&arr[i + 1], &arr[high]);
    return (i + 1);
}
void quickSort(int arr[], int low, int high)
{
    if (low < high)
    {
        /* pi is partitioning index, arr[p] is now
        at right place */
        int pi = partition(arr, low, high);

        // Separately sort elements before
        // partition and after partition
        quickSort(arr, low, pi - 1);
        quickSort(arr, pi + 1, high);
    }
}
void printArray(int arr[], int size)
{
    int i;
    for (i = 0; i < size; i++)
        cout << arr[i] << " ";
    cout << endl;
}

int main()
{
    int n,count=0;
    cin>>n;
    int *arr= new int[n];
    for(int i=0;i<n;i++)
    {
        cin>>arr[i];
    }

    quickSort(arr,0,n-1);
    //printArray(arr,n);
    for(int i=0;i<n-1;i+=2)
    {
      count+=arr[i+1]-arr[i];
    }
    cout<<count;
    return 0;
}

#include<iostream>
#include<algorithm>
using namespace std;

/*void swap(int *a, int*b)
{
    int tmp=*a;
    *a=*b;
    *b=tmp;
}
int partition (int arr[], int low, int high)
{
    int pivot = arr[high]; // pivot
    int i = (low - 1); // Index of smaller element

    for (int j = low; j <= high - 1; j++)
    {
        // If current element is smaller than the pivot
        if (arr[j] < pivot)
        {
            i++; // increment index of smaller element
            swap(&arr[i], &arr[j]);
        }
    }
    swap(&arr[i + 1], &arr[high]);
    return (i + 1);
}
void quickSort(int arr[], int low, int high)
{
    if (low < high)
    {
        pi is partitioning index, arr[p] is now
        at right place
        int pi = partition(arr, low, high);

        // Separately sort elements before
        // partition and after partition
        quickSort(arr, low, pi - 1);
        quickSort(arr, pi + 1, high);
    }
}*/
void printArray(int arr[], int size)
{
    int i;
    for (i = 0; i < size; i++)
        cout << arr[i] << " ";
    cout << endl;
}

int main()
{
    int n,count=0;
    cin>>n;
    int *arr= new int[n];
    for(int i=0;i<n;i++)
    {
        cin>>arr[i];
    }

    sort(arr,arr+n);
   //printArray(arr,n);
   // cout<<endl;
    for(int i=0;i<n-1;i+=2)
    {
      count+=arr[i+1]-arr[i];
    }
    cout<<count;
    return 0;
}

/*
Problem:
	Sort array of integer (A)
Algorithm:
	Step1: Divide the input array into two subarrays of roughly equal size.
	Step2: Recursively mergesort each of the subarrays.
	Step3: Merge the newly-sorted subarrays into a single sorted array

	MergeSort(A[1 .. n]):	{correct=>doNothing} 		, if n = 1
							{m = n/2
							 MergeSort(A[1 .. m]
							 MergeSort(A[m+1 .. n])	, if n > 1
							 Merge(A[1 .. n], m)}
Complexity:
	O(nlogn)
Specific problem: https://codeforces.com/problemset/problem/1092/B
*/

#include <iostream>
#include <array>

const int MAXN = 1e6+1;
int B[MAXN];
void Merge(int A[], int l, int r, int m) {
	int i = l, j = m+1;
	for(int k = l; k <= r; k++)
		if(i > m) {
			B[k] = A[j]; j++;
		}
		else if(j > r) {
			B[k] = A[i]; i++;
		}
		else if(A[i] > A[j]) {
			B[k] = A[j]; j++;
		}
		else {
			B[k] = A[i]; i++;
		}
	for(int k = l; k <= r; k++)
		A[k] = B[k];
}

void MergeSort(int A[], int l, int r) {
	if(l == r)
		return;
	int m = (r+l)/2;
	MergeSort(A, l, m);
	MergeSort(A, m+1, r);
	Merge(A, l, r, m);
}

int A[MAXN];
int main(){
	int n;
	scanf("%d", &n);
	for(int i = 0; i < n; i++)
		scanf("%d", A+i);
	MergeSort(A, 0, n-1);
	int ans = 0;
	for(int i = 0; i < n; i+=2)
		ans += (A[i+1] - A[i]);
	printf("%d\n", ans);
	return 0;
}

#include <bits/stdc++.h>
using namespace std;

int main() {
	int ilestudentow, wynik;
	cin >> ilestudentow;
	int skills[ilestudentow+1];
	for(int i=0; i<ilestudentow; i++){
		cin >> skills[i];
	}
	sort(skills, skills + ilestudentow);
	for(int i = 0; i<ilestudentow;){
	if(skills[i]==skills[i+1]){
		 i=i+2;
	}
	else {
		wynik=wynik+(skills[i+1]-skills[i]);
		 i=i+2;
	}}
	cout << wynik;
	return 0;
}

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main()
{
  int n;
  cin >> n;

  vector<int> vec;

  for (int i = 0; i < n; i++)
  {
    int temp;
    cin >> temp;
    vec.push_back(temp);
  }

  sort(vec.begin(), vec.end());
  // sort the vector*

  int sum = 0;
  for (int i = 0; i < n; i++)
  {
    sum += (vec[i+1] - vec[i]);
    i++;
  }

  cout << sum << endl;

}

#include<iostream>
#include<algorithm>
using namespace std;
int main()
{
	int n,a[100000],i;
	int t,x[100000],k=0,sum=0;
	cin>>n;
	for(i=0;i<n;i++)
	{
		cin>>a[i];
	}
	sort(a,a+n);
	for(i=0;i<n/2;i++)
	{
		t=i*2;
		x[k]=a[t+1]-a[t];
		//cout<<"x:"<<x;
		sum=sum+x[k];
		k++;
	}
	cout<<sum<<endl;
return 0;
}

#include<iostream>
#include <algorithm>
using namespace std;

int main()
{
    int num, sum = 0;
    int arr[101];
    cin >> num;
    int i = 0;
    for (; i < num; i++)
        cin >> arr[i];
    sort(arr, arr + num);
    for (int j = 0; j < i - 1; j += 2)
    {
        sum += arr[j + 1] - arr[j];
    }
    cout << sum;
    return 0;
    }

#include <iostream>
#include <stdlib.h>
using namespace std;

int*b;

void minisort(int * &a, int first1, int last1, int last2){
  int f1=first1, l1=last1, f2=last1+1, l2=last2, n=0;
  while (n<last2-first1+1){
    while ((a[f1]<=a[f2] || f2>l2)  && f1<=l1){
      b[n++]=a[f1++];
    }
    b[n++]=a[f2++];
  }
  for (int i=0;i<n;i++){
    a[i+first1]=b[i];
  }
}

void sort(int * &a, int first, int last){
  if (first >= last)
    return;
  int mid = first + (last - first) / 2;
  sort(a, mid+1, last);
  sort(a, first, mid);
  minisort(a, first, mid, last);
}

int main() {
  int n, res=0;
  cin >>n;
  int*a=(int*)calloc(n, sizeof(int));
  b=(int*)calloc(n, sizeof(int));
  for (int i=0;i<n;i++){
    cin >>a[i];
  }
  sort (a, 0, n-1);
  for (int i=1;i<n;i+=2){
    res+=(a[i]-a[i-1]);
  }
  cout <<res;
  return 0;
}

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int main() {
    int n;
    cin >> n;

    vector<int> a(n);
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }

    sort(a.begin(), a.end());
    int ans = 0;
    for (int i = 0; i < n; i += 2) {
        ans += a[i + 1] - a[i];
    }
    cout << ans << endl;
    return 0;
}

#include <iostream>
#include <algorithm>

int main() {
    int n; std::cin >> n;
    int s[n]; for(int i = 0; i < n; i++) std::cin >> s[i];
    std::sort(s, s+n);
    int output = 0;
    for(int i = 0; i < n-1; i += 2) {
        output += std::abs(s[i] - s[i+1]);
    }
    std::cout << output;
}

    #include <bits/stdc++.h>
    using namespace std;

    #define SZ size()
    #define MIN LLONG_MIN
    #define MAX LLONG_MAX
    #define M 1000000007
    #define MP make_pair
    #define F first
    #define S second
    #define endl "\n"

    #define pb push_back
    #define N 100005

    typedef long long  ll;
    typedef unsigned long long ull;

    typedef vector<int> vi;
    typedef vector< vi > vvi;
    typedef vector<ll> vll;
    typedef vector<string> vs;
    typedef pair<int, int> pii;
    typedef map<int, int> mii;
    typedef map<char, int> mci;
    typedef map<string, int> msi;

    int main(){
        ios_base::sync_with_stdio(false);
        cin.tie(NULL);
        cout.tie(NULL);
    	// code part
    	int n; cin >>n; int a[N];int s=0;
    	for(int i =0; i <n; i++) cin >>a[i];
    	sort(a, a+n);
    	for(int i =0; i <n; i+=2) {
    	    s+=(a[i+1] - a[i]);
    	}
    	cout <<s;
    	return 0;
    }

#include<iostream>
using namespace std;
int main()
{
	int n, *a, s = 0;
	cin >> n;
	a = new int[n];
	for (int c = 0; c < n; c++)
		cin >> a[c];
	for (int c = 0; c < n; c++)
	for (int j = 0; j < n - 1; j++)
	if (a[j]>a[j + 1])
		a[j] ^= a[j + 1] ^= a[j] ^= a[j + 1];
	for (int c = 0; c < n; c += 2)
		s += a[c + 1] - a[c];
	cout << s ;
}

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

vector<int>::iterator partitionx(vector<int>::iterator first, vector<int>::iterator last){
    int v = *(first + distance(first, last) / 2);
    last--;
    while (distance(first, last) >= 0){
        while (*first < v) first++;
        while (*last > v) last--;
        if (*first == v && *last == v){
            first ++;
        }
        if (distance(first, last) > 0) {
            swap(*first, *last);
        }
    }
    return last;
}

void Qsort(vector<int>::iterator first, vector<int>::iterator last){
    vector<pair<vector<int>::iterator, vector<int>::iterator>> Q;
    Q.push_back(make_pair(first, last));
    while (!Q.empty()){
        auto iters = Q[Q.size() - 1];
        Q.pop_back();
        auto mid = partitionx(iters.first, iters.second);
        if (distance(iters.first, mid) > 1) Q.push_back(make_pair(iters.first, mid));
        if (distance(mid, iters.second) > 1) Q.push_back(make_pair(mid, iters.second));
    }
}

int main(){
    int n, s = 0;
    cin >> n;
    vector <int> a (n);
    for (int i = 0; i < n; ++i) cin >> a[i];
    //auto x = partitionx(a.begin(), a.end());
    Qsort(a.begin(), a.end());
    for (int i = 0; i < n; i+= 2) s += a[i + 1] - a[i];
    cout << s;
    //cout << endl << *x << ' ' << distance(a.begin(), x) + 1;
    return 0;
}

#include<iostream>
#include<cmath>
using namespace std;
int num[10000000]={0};
int temp,le,ri,mid;
void fsort(int l,int r)
{
    le=l;
    ri=r;
    mid=num[(le+ri)/2];
    while(le<=ri)
    {
        while(num[le]<mid)le++;
        while(num[ri]>mid)ri--;
        if(le<=ri)
        {
            temp=num[ri];
            num[ri]=num[le];
            num[le]=temp;
            le++;
            ri--;
        }
    }
    if(le<r)fsort(le,r);
    if(l<ri)fsort(l,ri);
}
/*int solve(int l,int r)
{
	int sum=0;
	for(int i=l;i<=r;i++)
	{
		sum+=num[i];
	}
	int avg=sum/(r-l+1);
	int ans=0;
	for(int i=l;i<=r;i++)
	{
		ans+=abs(num[i]-avg);
	}
	return ans;
}*/
int main()
{
	int n;
	cin>>n;
	for(int i=0;i<n;i++)
	{
		cin>>num[i];
	}
	fsort(0,n-1);
	//for(int i=0;i<n;i++)cout<<num[i]<<' ';
	//cout<<endl;
	int a=0;
	for(int i=0;i<n/2;i++)
	{
		//cout<<num[i<<1]<<' '<<num[i<<1|1]<<' ';
		a+=num[i<<1|1]-num[i<<1];
	}
	cout<<a;
	return 0;
}

// codeForces_1092B.cpp : Этот файл содержит функцию "main". Здесь начинается и заканчивается выполнение программы.

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main()
{

	int size, sum = 0, i = 0;
	cin >> size;
	vector <int> array(size);
	for (; i < size; i++) {
		cin >> array[i];
	}
	i = 0;
	sort(array.begin(), array.end());
	while (i < size ) {
		if (array[i + 1] == array[i]) {
		}
		else if(array[i + 1] > array[i]){
			sum += array[i + 1] - array[i];
		}
		i += 2;
	}
	cout << sum;
}

#include<stdio.h>
#include<algorithm>
using namespace std;
int main()
{int n,a[105],ans=0;
scanf("%d",&n);
for(int i=0;i<n;i++)
	scanf("%d",&a[i]);
sort(a,a+n);
for(int i=0;i<n;i+=2)
	ans+=a[i+1]-a[i];
printf("%d",ans);}

                        //Bismillahir Rahmanir Rahim
#include <bits/stdc++.h>
using namespace std;

using ll = long long;

int main() {
    int i,n,a,b,c,res,ans=0,in;
    vector<int>v;
    cin>>n;
    for(i=0; i<n; i++) {
        cin>>in;
        v.push_back(in);
    }
    sort(v.begin(),v.end());
    for(i=1; i<v.size(); i=i+2) {
        ans += v[i]-v[i-1];
    }
    cout<<ans<<endl;
}

#include<bits/stdc++.h>
using namespace std;
int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int n,i,p=0;
    cin>>n;
    int arr[n];
    for(i=0;i<n;i++)
      cin>>arr[i];
    sort(arr,arr+n);
    for(i=1;i<n;i+=2)
      p+=arr[i]-arr[i-1];
    cout<<p;
    return 0;
}

#include<iostream>
#include<string>
#include<vector>
using namespace std;
int main()
{
    int n;
    cin>>n;
    int t=0;
    int count=0;
    vector<int> v(n);
    for(int i=0;i<n;++i)
    {
        cin>>v[i];
    }

    for(int i=0;i<v.size();++i)
    {
        for(int j=i+1;j<v.size();++j)
        {
            if(v[j]<v[i])
            {
                swap(v[i],v[j]);
                }
        }
        }
        for(int i=0;i<v.size();i+=2)
         {
       if(v[i]<v[i+1])
       {
           t=v[i+1]-v[i];
           v[i]+=t;
           count+=t;
           }
         }
      cout<<"\n"<<count;
}

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
int main(){
    long long n,a,sum=0,x;
    vector<int> que;
    cin>>n;
    while(n--){
        cin>>x;
        que.push_back(x);
    }

    sort(que.begin(),que.end());

    for(int i=0;i<que.size();i=i+2){
        sum+=que[i+1]-que[i];
    }
    cout<<sum;
}

#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int a[n];
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  sort(a, a + n);
  int ans = 0;
  for (int i = 0; i < n; i += 2) {
    ans += a[i + 1] - a[i];
  }
  cout << ans << "\n";
  return 0;
}

#include <bits/stdc++.h>
#include <climits>
using namespace std;

#define endl        '\n'
//#define IOS       ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define c0(x)       cout<<(x)<<" "
#define c1(x)       cout<<(x)<<endl
#define rep         for(ll i = 0 ; i < n ; i++)
#define f(i,s,n)    for(ll i = s ; i < n ; i++)
#define fe(i,s,n)   for(ll i = s ; i <= n ; i++)
#define rfe(i,s,n)  for(ll i = s ; i >= n ; i--)
#define TCs(x)      ll x; cin>>x; while(x--)
#define TC(x)       ll x=1; while(x--)
#define f2(it,v)    for(it = v.begin(); it != v.end(); ++it)
#define auto(m)     for(auto &it:m)
#define ip(n,a)     ll n;cin>>n;ll a[n];rep{cin>>a[i];}
#define ip2(n,a,b)  ll n;cin>>n;ll a[n];ll b[n];rep{cin>>a[i];} rep{cin>>b[i];}
//#define ip(n,a)   ll n;cin>>n;ll a[n];rep{cin>>a[i];}
#define op(n,a)     f(i,0,n){cout<<a[i]<<" ";}
#define i2p(n,k,a)  ll n,k;cin>>n>>k;ll a[n];rep{cin>>a[i];}
//#define ll        long long
//#define ld        long double
//#define vl        vector<ll>
#define mll         map<ll, ll>
#define mcl         map<char, ll>
#define msl         map<string, ll>
#define mp          make_pair
#define pii         pair<ll, ll>
#define pb          push_back
#define ff          first
#define ss          second
#define all(v)      v.begin(), v.end()
#define vsort(v)    sort(all(v))
#define vrsort(v)   reverse(all(v))
#define Max(x,y,z)  max(x,max(y,z))
#define Min(x,y,z)  min(x,min(y,z))
#define F           first
#define S           second
//#define ps(x,y)     fixed<<setprecision(y)<<x
//#define ps(x)       std::cout << std::fixed; std::cout << std::setprecision(x);
#define clz(a)      __builtin_clz(a) // count leading zeroes (geeksforgeeks.org/builtin-functions-gcc-compiler/)
#define ctz(a)      __builtin_ctz(a) // count trailing zeroes
//#define ctz(a)      __builtin_ctzll(a)
#define popc(a)     __builtin_popcount(a) // count set bits (for ints only diff for ll)
#define GCD(A,B)    __gcd(A,B)
//#define LCM(A,B)    boost::math::lcm(A,B)
//#define COUNT(v,x)    count(all(v),x)
//#define COUNT(v,x)    count(all(s),'x')

//Typedefs:-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
typedef long long ll;
typedef long double ld;
//typedef pair<int,int> pii;
typedef pair<long long,long long> pll;
typedef pair<string,string> pss;
typedef vector<int> vi;
typedef vector<long long> vl;
typedef pair<ll, ll> pairs;
//typedef vector<pair<ll, pair<ll, ll>>> vppl;

const int N = 1e5 + 5;
const long long MOD=(long long)(1e9+7);
const long long INIT=(long long)(1e6+1);
//Functions:----------------------------------------------------------------------------------------------------------------------------------------------------------------------
inline string IntToString(ll a)
{
    char x[100];
    sprintf(x, "%lld", a);
    string s = x;
    return s;
}
//....................................................................................//
inline ll StringToInt(string a)
{
    char x[100];
    ll res;
    strcpy(x, a.c_str());
    sscanf(x, "%lld", &res);
    return res;
}
//....................................................................................//
inline string GetString(void)
{
    char x[1000005];
    scanf("%s", x);
    string s = x;
    return s;
}
//....................................................................................//
inline string uppercase(string s)
{
    int n = s.size();
    f(i,0, n)
    if (s[i] >= 'a' && s[i] <= 'z')
        s[i] = s[i] - 'a' + 'A';
    return s;
}
//....................................................................................//
inline string lowercase(string s)
{
    int n = s.size();
    f(i,0,n)
    if (s[i] >= 'A' && s[i] <= 'Z')
        s[i] = s[i] - 'A' + 'a';
    return s;
}
//....................................................................................//
inline void OPEN(string s)
{
#ifndef TESTING
    freopen((s + ".in").c_str(), "r", stdin);
    freopen((s + ".out").c_str(), "w", stdout);
#endif
}
//....................................................................................//

template<typename T, typename U>            // Same as max_val = max (max_val, val)
static inline void amin(T &x, U y)          // Same as min_val = min (min_val,val)
{
    if (y < x)                              //maximum = amax(max_val, val);
        x = y;                              //minimum = amin (min_val, val);
}
//....................................................................................//
template<typename T, typename U>
static inline void amax(T &x, U y)
{
    if (x < y)
        x = y;
}
//....................................................................................//
ll power(ll x,ll y)
{
    if (y == 0)
        return 1;
    ll p = power(x, y/2) % MOD;
    p = (p * p) % MOD;

    return (y%2 == 0)? p : (x * p) % MOD;
}
//....................................................................................//
int lcm(ll a, ll b)
{
    ll lar = max(a, b);
    ll small = min(a, b);
    for (ll i = lar; ; i += lar) {
        if (i % small == 0)
            return i;
    }
}
//....................................................................................//
int bsearch(ll arr[],ll l,ll r,ll x)
{
    while (l <= r)
    {
        ll m = l + (r - l) / 2;
        if (arr[m] == x){
            return m;
        }
        if (arr[m] < x){
            l = m + 1;
        }
        else
            r = m - 1;
    }
    return -1;
}
//....................................................................................//
template<typename T> T gcd(T a,T b) { if(a==0) return b; return gcd(b%a,a); }
template<typename T> T pow(T a,T b, ll m){T ans=1; while(b>0){ if(b%2==1) ans=(ans*a)%m; b/=2; a=(a*a)%m; } return ans%m; }
//int bsearch(ll arr[], ll l, ll r, ll x){while (l <= r){ll m = l + (r - l) / 2;if(arr[m] == x){return m;}if(arr[m] < x){l = m + 1;}else{r = m - 1;}}}
//Solve:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

void solve()
{
        ip(n,a);
        sort(a,a+n);
        ll ans=0;
        f(i,0,n)
        {
                if(i%2 == 0)
                {
                        ans+= a[i+1]-a[i];
                }
        }
        cout<<ans<<endl;

}

int main ()
{
        ios_base::sync_with_stdio(false);
        cin.tie(0);
        cout.tie(0);

#ifndef ONLINE_JUDGE
        freopen("input.txt","r",stdin);
        freopen("output.txt","w",stdout);
#endif

        TC(t)
        {
                solve();
        }
        return 0;
}

#include<bits/stdc++.h>

typedef long long int ll;
typedef unsigned long long int ull;

#define dbg printf("in\n")
#define nl printf("\n")
#define N 100100

#define sf(n) scanf("%d", &n)
#define sff(n,m) scanf("%d%d",&n,&m)
#define sfl(n) scanf("%I64d", &n)
#define sffl(n,m) scanf("%I64d%I64d",&n,&m)

#define pf(n) printf("%d",n)
#define pff(n,m) printf("%d %d",n,m)
#define pffl(n,m) printf("%I64d %I64d",n,m)
#define pfl(n) printf("%I64d",n)
#define pfs(s) printf("%s",s)

#define pb push_back
#define pp pair<ll,char>

using namespace std;

int main()
{
    //freopen("in.txt", "r", stdin);

    int i,j,k;
    int n,m,t;

    sf(n);
    int a[n];

    for(i=0;i<n;i++){
        sf(a[i]);
    }

    sort(a,a+n);

    int cnt=0;
    for(i=0;i<n;i+=2)
        cnt+=(a[i+1]-a[i]);

    pf(cnt);

    return 0;
}

#include <cstdio>

int main()
{
   int N, t, ans;
   int a[200];
   scanf("%d",&N);
   for(int i = 0; i<N; ++i)scanf("%d", a+i);

   for(int i= 0; i<N;++i)
   for(int j =i+1;j<N;++j)
   if (a[i] > a[j]){
      t = a[i]; a[i] = a[j]; a[j] = t;
   }

   ans = 0;
   for(int i = 0; i < N; i +=2 ){
      ans += a[i+1] - a[i];
   }

   printf("%d\n", ans);

   return 0;
}

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <ctime>
#include <random>
#include <iomanip>

#include <algorithm>
#include <vector>
#include <queue>
#include <string>
#include <stack>
#include <set>
#include <map>
#include <numeric>
#include <functional>
#include <deque>
#include <array>
#include <iterator>
#include <bitset>
#include <initializer_list>

using namespace std;

#include <ext/rope>

using namespace __gnu_cxx;

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace __gnu_pbds;

#define int long long

typedef pair<int, int> PII;
typedef vector<int> VI;
typedef vector<PII> VPI;

#define add push_back
#define rem pop_back
#define ALL(x) x.begin(), x.end()
#define SORT(x) sort(ALL(x))
#define SZ(x) int((x).size())
#define F first
#define S second
#define DEBUG(x) cout << #x << " " << x << endl;
#define forn(i, a, b) for(int i = a; i <= b; i++)

const double EPS = 1e-9;
const double PI = acos ( -1. );
const int MOD = 1e9 + 7;
const int MAXN = 500001;
int INF = __INT64_MAX__;
int MAX = -1e18;
int MIN = 1e18;
string YN[] = {"NO", "YES"};

#define gcd(a, b) __gcd(a, b)
#define lcm(a, b) ((a)*((b)/gcd(a,b)))

inline int GCD_E ( int a, int b, int & x, int & y )
{
        if ( !a ) {
                x = 0;
                y = 1;
                return b;
        }
        int x1, y1;
        int d = GCD_E ( b % a, a, x1, y1 );
        x = y1 - ( b / a ) * x1;
        y = x1;
        return d;
}

inline int divMOD ( int a, int b, int m = MOD )
{
        int x, y;
        int g = GCD_E ( b, m, x, y );
        x = ( x % m + m ) % m;
        return ( a * x ) % m;
}

int px[] = { 1, 1, -1, -1 };
int py[] = { -1, 1, -1, 1};
int dx[] = { 1, 0, -1, 0, 1, 1, -1, -1 };
int dy[] = { 0, 1, 0, -1, 1, -1, 1, -1 };
int fx[] = {-2, -2, -1, -1,  1,  1,  2,  2};
int fy[] = {-1,  1, -2,  2, -2,  2, -1,  1};

template<typename T1, typename T2> auto max ( T1 a, T2 b ) { auto max = a > b ? a : b; return max; }
template<typename T1, typename T2> auto min ( T1 a, T2 b ) { auto min = a < b ? a : b; return min; }

int POW ( int a, int n, int m = MOD )
{
        int res = 1;
        while ( n ) {
                if ( n & 1 )
                        res = ( res * a ) % m;
                a = ( a * a ) % m;
                n >>= 1;
        }
        return res;
}

//tree<int, null_type, less_equal<int>, rb_tree_tag, tree_order_statistics_node_update> tr;

vector<int> vc;

string s, t;

set<int> st;

map<int, int> mp;

static const int N = 1 << 20;
static const int M = 123456;

static int n, m, k, res, cnt;
static int A[N], B[N];

void solution()
{
        cin >> n;
        forn ( i, 1, n ){
                cin >> A[i];
        }
        sort( A + 1, A + 1 + n );
        for ( int i = 1; i <= n; i += 2 ){
                cnt += A[i + 1] - A[i];
        }
        cout << cnt;

}

__INT16_C() main ( __int32 argc, char * argv[] )
{

        //freopen("input.txt", "r", stdin);
        //freopen("output.txt", "w", stdout);

        ios_base::sync_with_stdio ( false ); cin.tie ( nullptr ); cout.tie ( nullptr );
        //cout.precision(15);

        int query = 1;
        // cin >> query;

        while ( query-- ) solution();

}

#include<stdio.h>

void merge(int left, int mid, int right, int data[]){
	int sl = left;
	int sr = mid+1;
	int temp[1000];
	int st = 0;
	while(sl <= mid && sr <= right){
		if(data[sl]<data[sr]){
			temp[st++]=data[sl++];
		}else{
			temp[st++]=data[sr++];
		}
	}
	while(sl<=mid){
		temp[st++]=data[sl++];
	}
	while(sr<=right){
		temp[st++]=data[sr++];
	}
	for(int i = left,j=0;i<=right;i++,j++){
		data[i]=temp[j];
	}
}

void mergeSort(int left,int right, int data[]){
	if(left == right) return;
	int mid = (left+right)/2;
	mergeSort(left,mid,data);
	mergeSort(mid+1,right,data);
	merge(left,mid,right,data);
}
int abs(int a){
	if(a<0) return -a;
	return a;
}
int main(){
	int nc,temp[1000],hasil=0;
	scanf("%d",&nc);
	for(int i = 0;i<nc;i++){
		scanf("%d",&temp[i]);
	}
	mergeSort(0,nc-1,temp);
	for(int i = 0;i<nc-1;i+=2){
		hasil = hasil + abs(temp[i]-temp[i+1]);
	}
	printf("%d\n",hasil);
}

#include <iostream>
#include <vector>
using namespace std;

typedef vector<int> vi;

void Merge(vi& left, vi& right, vi& fin)
{
	int i = 0, j = 0, k = 0;
	int nL = left.size();
	int nR = right.size();
	while (i < nL && j < nR)
	{
		if (left[i] <= right[j])
		{
			fin[k] = left[i];
			i++;
		}
		else
		{
			fin[k] = right[j];
			j++;
		}
		k++;
	}
	while (i < nL)
	{
		fin[k] = left[i];
		i++;
		k++;
	}
	while (j < nR)
	{
		fin[k] = right[j];
		j++;
		k++;
	}
}

void MergeSort(vector<int>& res)
{
	int n = res.size();
	if (n > 1)
	{
		int mid = n / 2;
		vector<int> left(mid);
		vector<int> right(n - mid);
		for (int i = 0; i < mid; i++)
		{
			left[i] = res[i];
		}
		for (int i = mid; i < n; i++)
		{
			right[i - mid] = res[i];
		}
		MergeSort(left);
		MergeSort(right);
		Merge(left, right, res);
	}
	return;
}

int main()
{
	std::ios::sync_with_stdio(false);
	int p;
	cin >> p;
	vector<int> x(p);
	int count = 0;
	for (int i = 0; i < p; i++)
	{
		int Ai;
		cin >> Ai;
		x[i] = Ai;

	}
	MergeSort(x);
	for (int i = 0; i < p - 1; i += 2)
	{
		count += x[i + 1] - x[i];
	}
	cout << count << endl;

	return 0;
}

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

int main() {
        int n;
        cin>>n;
        int a[n];
        for(int i=0;i<n;i++)
            cin>>a[i];
        sort(a,a+n);
    int c=0;
        for(int i=0;i<n-1;i=i+2){
            c=c+abs(a[i]-a[i+1]);
        }
         cout<<c<<endl;
    return 0;
}

#include<iostream>
#include<algorithm>
using namespace std;
bool cmp(const long long&a,long long&b)
{
	return a<b;
}
int main()
{
	int n,a[200];
	while(cin>>n)
	{
		for(int i=0;i<n;i++)
			cin>>a[i];
		sort(a,a+n);

		int s=0;
		for(int i=0;i<n;i+=2)
		{
			s+=a[i+1]-a[i];

		}
		cout<<s<<endl;

	}

}

#include <iostream>
using namespace std;
int main()
{
	int n,*A,i=0,j=0,a,b=0;
	cin>>n;
	A=new int[n];
	for(i=0;i<n;i++)
		cin>>A[i];
	for(i=0;i<n;i++)
	{
		for(j=0;j<n;j++)
		{
			if(A[i]<A[j])
			{
				a=A[i];
				A[i]=A[j];
				A[j]=a;
			}
		}
	}
	for(int k=0;k<n-1;)
	{
		a=A[k+1]-A[k];
		b+=a;
		k+=2;
	}
	cout<<b;
	return 0;
}

// ConsoleApplication8.cpp : Defines the entry point for the console application.
//

//#include "stdafx.h"
#include <iostream>
#include <map>
#include<string>
using namespace std;

map<int, int>MyMap;
int main()
{
	int Size, n;
	cin >> Size;
	for (int i = 0; i < Size; i++)
	{
		cin >> n;
		MyMap[n]++;
	}

	int Sum = 0;
	for (map<int, int>::iterator it = MyMap.begin(); it != MyMap.end(); it++)
	{
		if (it->second % 2 != 0)
		{
			map<int, int>::iterator it1 = it;
			it1++;
			for (; it1 != MyMap.end(); it1++)
			{
				if (it1->second % 2 != 0)
				{
					Sum += abs(it->first - it1->first);
					it1->second = 2;
					it = it1;
					break;
				}
			}
		}
	}
	cout << Sum;
	//system("pause");
	return 0;
}

#include <bits/stdc++.h>

using namespace std;

int main()
{
    int n;
    cin>>n;
    int a[101];
    for(int i=0 ;i<n ; i++)
        cin>>a[i];
    sort(a,a+n);
    int ans=0;
    for(int i=0 ; i<n ; i+=2)
        ans+=a[i+1]-a[i];
    cout<<ans<<endl;
}

#include<iostream>
#include<algorithm>
using namespace std;
int a[1000];
int ans1,ans2;
int main() {
	int n;
	cin >> n;
	for (int i = 0;i < n;i++) {
		cin >> a[i];
	}
	sort(a, a + n);
	for (int i = 0;i < n;i+=2) {
		ans1 = abs(a[i] - a[i+1]);
		ans2 = ans2 + ans1;
	}
	cout << ans2;
	return 0;
}

#include<bits/stdc++.h>
using namespace std;

int main(){

	int n; cin >> n;
	int a[n];

	for(int i = 0; i < n; i++) cin >> a[i];

	sort(a, a+n);

	int ans = 0;

	for(int i = 0; i < n-1; i+=2) ans += a[i+1]-a[i];

	cout << ans;

	return 0;
}

#include<bits/stdc++.h>
using namespace std;
#define FOR(i,a,b) for(int i=a;i<=b;i++)
main()
{
    int a[105];
    int n;cin>>n;
    FOR(i,1,n) cin>>a[i];
    sort(a+1,a+n+1);
    int res=0;
    for(int i=1;i<=n;i+=2)
    {
        res+=a[i+1]-a[i];
    }
    cout<<res;
}

#include<bits/stdc++.h>

using namespace std;

int a[200];
int main()
{
    int n,x,j;
    cin>>n;
    for (int i=0; i<n; i++)
    {
        cin>>x;
        a[x]++;
    }
    int k=0;
    x=0;
    j=0;
    for (int i=1; i<=100; i++)
    {
        if (x==0 && a[i]%2==1)
        {
            x=a[i];
            j=i;
            continue;
        }
        if ((a[i]%2)==1)
        {
            k+=min(x,a[i])*(i-j);
            x=max(a[i],x)-min(a[i],x);
            j=i;
        }
    }
    cout<<k;
    return 0;
}

/******************************************************************************

Welcome to GDB Online.
GDB online is an online compiler and debugger tool for C, C++, Python, PHP, Ruby,
C#, VB, Perl, Swift, Prolog, Javascript, Pascal, HTML, CSS, JS
Code, Compile, Run and Debug online from anywhere in world.

*******************************************************************************/
#include <iostream>
#include <algorithm>
using namespace std;
 int a[100];
int main()
{
    int n,i,l;
  cin>>n;
   for(i=0;i<n;i++)
   cin>>a[i];
   sort(a,a+n);
      for(i=0;i<n;i=i+2)
      {
        l=l+a[i+1]-a[i];
      }
  cout<<l;
}

#include <bits/stdc++.h>
using namespace std;
const int N = 100;
int a[N];

int main() {
	int n , cnt = 0;;
	cin >> n;
	for (int i = 0; i < n; ++i) {
        cin >> a[i];
	}
	sort(a , a + n);
	for (int i = 0; i < n; i += 2) {
        if (a[i + 1] - a[i] >= cnt) {
            cnt += a[i + 1] - a[i];
        }
	}
	cout << cnt;
}

#include <stdio.h>
#include <math.h>

int main()
{
    int n;
    scanf("%d",&n);
    int a[n];
    for(int i=0;i<n;i++){
        scanf("%d",&a[i]);
    }
    int sum=0;
    for(int i=0;i<n/2;i++){
        long long  int temp=10000000000;
        for(int j=0;j<n;j++){
            if(i==j){
                continue;
            }
            if(fabs(a[i]-a[j])<=temp){
                temp=fabs(a[i]-a[j]);
            }
        }
        sum=sum+temp;
    }
    printf("%d\n",sum);
    return 0;
}

#include<bits/stdc++.h>
#define ll long long
#define r(i,n) for(ll i=0;i<n;i++)
#define rp(i,a,b) for(ll i=a;i<b;i++)
#define rt return
#define db double
#define vd void
#define p(x) cout<<(x)<<endl;
#define ce continue;
#define bl bool
#define r0 rt 0;
#define r1 rt 1;
#define elif else if
#define bk break;
#define A p("A")
#define B p("B")
#define C p("C")
#define D p("D")
#define E p("E")
#define Sort(a) sort(a.begin(),a.end());
#define Reverse(a) reverse(a.begin(),a.end());
#define kaigyo cout<<endl;
#define pb(x) push_back(x);
using namespace std;
void Cond(int g){if(g)p("YES")else p("NO")rt;}
void cond(int g){if(g)p("Yes")else p("No")rt;}
ll power(ll k){ll t=1;r(i,k+1)t*=2;rt t;}
ll comb(ll i,ll j){ll up=1;for(ll n=i;n>i-j;n--){up*=n;}ll down=1;for(ll r=j;r>=1;r--)down*=r;rt up/(down);}//nCr.
ll gcd(ll a,ll b){if(a<b)swap(a,b);if(a%b==0)rt b;gcd(b,a%b);}
ll Digits(ll k){ll t=0;while(k){t+=k%10;k/=10;}rt t;}
char m1[26]={'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
char m2[26]={'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
char m3[10]={'0','1','2','3','4','5','6','7','8','9'};
const ll INF=(ll)1e18;
const ll MAX=(ll)1e5+10;
const ll NIL=-1;
struct Node{ll p,l,r;};
typedef struct edge{ll to,cost;}EDGE;
typedef pair<ll,ll> P;
#define ldb long double
ll ans=0,ct=0,ct1=0,ct2=0,cnt=0,tmp=0,g=0,n=0,m=0;
ll tmp1=0,tmp2=0,tmp3=0,tmp4=0,sum=0,pos=0,k=0;
ll len=0,len1=0,len2=0,len3=0,len4=0,len5=0;
ll mx=-INF,mn=INF;ll x;
map<ll,ll>mp,mp1,mp2;
set<P>st,st1,st2;
const ll MOD=((ll)1e9+7);

int main(){
cin>>n;
vector<ll>a(n);
r(i,n)cin>>a[i];
ans=0;
r(i,n){mn=INF;
	r(j,n){
	if(i==j||mp[j]||mp[i])ce
	if(abs(a[i]-a[j])<=mn){mn=abs(a[i]-a[j]);g=j;}
	}
	ans+=(mn!=INF)?mn:0;mp[i]=mp[g]=1;
}
p(ans)

	r0

}//main

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n,arr[103]={0},Max = INT_MIN;
    cin>>n;
    for(int i=0;i<n;i++) cin>>arr[i];
    sort(arr,arr+n);
    for(int i=0;i<n;i+=2){
        int diff = arr[i+1] - arr[i];
        if(diff>Max)
            Max = diff;
    }
    cout<<Max<<endl;
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n,i,j,sum=0;
    cin>>n;
    int arr[n];
    for(i=0;i<n;i++)
    {
        cin>>arr[i];
    }
    sort(arr,arr+n);
    for(i=0;i<n-1;i++)
    {
        for(j=1;j<=arr[i+1];j++)
        {
            if(arr[i]!=arr[i+1])
            {
                arr[i]++;
                sum++;
            }
            else
                break;
        }
    }
    return 0;
}

// Example program
#include <iostream>
#include <cmath>
#include <string>
using namespace std;
int main()
{
    int n,d,mkz=0,min=100;
    cin >> n;
    int a[n];
    for (int i=0;i<n;i++) {
        cin >> a[i];
    } for (int i=0;i<n/2;i++) {
        min=100;
       for (int j=0;j<n;j++) {
           if(i!=j) {
           d=abs(a[i]-a[j]);
           }
             if( d<min) {
                 min=d;
             }
       }
       mkz=mkz+min;
    }
    cout << mkz ;
    return 0;

}

#include<iostream>
using namespace std;
int main(){
	int n ; cin >> n;
	int mas[n];
	int sum1 = 0;
	int sum2 = 0;

	for(int i = 1;i <= n; i++){

		cin >> mas[i];

		if(i <= n / 2)sum1+=mas[i];
		if(i > n / 2 && i <= n)sum2+=mas[i];

	}

	cout<<max(sum1,sum2)-min(sum1,sum2);
	return 0;
}

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define n1 1000000
//#define fast ios_base::sync_with_stdio(false); cin.tie(NULL);
//fflush(stdout)
int main()
{
    //fast
ios_base::sync_with_stdio(false); cin.tie(NULL);
ll n;
cin>>n;
ll a[n1];
for(ll i=0;i<n;i++)
{
	cin>>a[i];
}
int ans=0;
for(int i=0;i<n;i++)
{
	if(a[i]==0)
	{
		continue;
	}
	int no=a[i];
	int index=0;
	int dif=INT_MAX;
	int k=i;
	for(int j=0;j<n;j++)
	{
		int c=abs(a[j]-no);
		if(j!=k && c<dif)
		{
			dif=c;
			index=j;
		}
	}
	a[i]=0;
	a[index]=0;
    ans+=dif;
}
cout<<ans<<endl;

return 0;
}

#include <bits/stdc++.h>

using namespace std;

int main()
{
    int n, sum = 0;

    cin >> n;

    int x[n+2];

    for(int i = 0; i <  n; i++)
    {
        cin >> x[i];
    }

    sort(x, x + n);

    x[n++] = 0;

    for(int i = 0; i < n ; i += 2)
    {

        sum += x[i+1] - x[i];

    }

    cout << sum << endl;

    return 0;
}

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n,arr[103]={0},Max = INT_MIN;
    cin>>n;
    for(int i=0;i<n;i++) cin>>arr[i];
    sort(arr,arr+n);
    for(int i=1;i<n;i++){
        int diff = arr[i] - arr[i-1];
        if(diff>Max)
            Max = diff;
    }
    cout<<Max<<endl;
    return 0;
}

#include <stdio.h>

struct kb{
    int dizi[256];
};

kb sdizi[1024];

int main(){}

#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
const int N=105;
int data[N];
int n,sum;
int main()
{
	ios::sync_with_stdio(false);cin.tie(0);
	cin>>n;
	for(int i=0;i<n;i++) scanf("%d",&data[i]);
	sort(data,data+n);
	for(int i=0;i<n;i+=2) sum+=data[i+1]-data[i];
	cout<<sum<<'\n';
	return 0;
}

#include <iostream>
#include <algorithm>

int main() {
    int n; std::cin >> n;
    int s[n]; for(int i = 0; i < n; i++) std::cin >> s[i];
    std::sort(s, s+n);
    for(int i : s) {
        std::cout << i << " ";
    }
    int output = 0;
    for(int i = 0; i < n-1; i += 2) {
        output += std::abs(s[i] - s[i+1]);
    }
    std::cout << output;
}

#include<bits/stdc++.h>
using namespace std;

int main(){
       int n,sum=0;
       cin>>n;
       int arr[n];
       for(int i=0; i<n;i++){
              cin>>arr[i];
       }
       sort(arr,arr+n);
       for(int i=1;i<n;i++){
              int x=abs(arr[i]-arr[i-1]);
              sum+=x;
       }
       cout<<sum<<endl;
}

#include<bits/stdc++.h>
using namespace std;
typedef vector<int> vi;
typedef vector< vector<int> > vii;
typedef vector<string> vs;
typedef unordered_map<int, int> uii;
typedef unordered_map<char, int> uci;
typedef unordered_map<string, int> usi;

int skillsDeterminer(vi skills) {
    vector < pair<int, int> > studentTeams;
    for(int i = 0; i < skills.size(); i++) {
        int currentPerson = skills[i];
        int diff = 10000;
        int secondPerson = 0;
        for(int j = 0; j < skills.size(); j++) {
            if(j!=i && skills[j]!=-1 && skills[i]!= -1) {
                int newDiff = abs(skills[i]-skills[j]);
                if(newDiff < diff) {
                    diff = newDiff;
                    secondPerson = j;
                }
            }
        }
        studentTeams.push_back(make_pair(currentPerson,skills[secondPerson]));
        skills[i] = -1;
        skills[secondPerson] = -1;
    }
    int minQues = 0;
    for(int i = 0; i < studentTeams.size(); i++) {
        if(studentTeams[i].first == -1 && studentTeams[i].second == -1) {
            continue;
        }
        else {
            int diff = abs(studentTeams[i].first - studentTeams[i].second);
            minQues += diff;
        }
    }

    return minQues;

}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int students;
    cin>>students;
    vi skills(students);
    for(int i = 0; i < students; i++) {
        cin>>skills[i];
    }
    int minSkills = skillsDeterminer(skills);
    cout<<minSkills;
    return 0;
}

#include <bits/stdc++.h>
using namespace std;

const int N = 1e2 + 7;
bool arr[N];
int n;

int main() {
  ios::sync_with_stdio(0);
  cin.tie(0); cout.tie(0);

  cin >> n;
  for (int i = 0; i < n; ++i) {
    int act;
    cin >> act;
    arr[act] ^= 1;
  }
  int res = 0;
  for (int i = 0; i < 101; ++i) {
    res += !arr[i];
  }
  cout << res << "\n";

  return 0;
}

#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for (int i=a; i<b; ++i)
#define per(i,a,b) for (int i=a; i>=b; --i)
#define Z(a) (int)(a).size()
#define all(i) (i).begin(),(i).end()
#define pb push_back
#define I first
#define II second
typedef vector<int> VI;
typedef long long ll;
typedef pair<int,int> PII;
typedef double db;
// head

int n,h; VI ipt;

int main() {
	scanf("%d",&n);
	rep(i,0,n) scanf("%d",&h), ipt.pb(h);
	sort(all(ipt));

	int mx=0;
	rep(i,1,n) mx+=ipt[i]-ipt[i-1];
	printf("%d",mx);
}

#include<bits/stdc++.h>
using namespace std;

main()
{
    int n;
    cin>>n;
    int a[100];
    for(int i=1;i<=n;i++)
        cin>>a[i];
    sort(a,a+n);
    int dem=0;
    for(int i=1;i<=n;i+=2)
        dem+=abs(a[i]-a[i+1]);
    cout<<dem;
}

#include <bits/stdc++.h>
using namespace std;

void swap(int a,int b)
{
    int temp=a;
    a=b;
    b=temp;
}

void bubblesort(int c[],int n1)
{
    for (int i=0;i!=n1-1;i++)
    {
        for (int j=0;j!=n1-i-1;j++)
        {
            if(c[j]<=c[j+1])
            {
                swap(c[j],c[j+1]);

            }
        }
    }

}

int main()
{
    int n;
    cin>>n;
    int a[n];
    for (int i=0 ;i!=n;i++)
    {
        cin>>a[i];

    }
    bubblesort(a,n);
    int sum=0;
    for (int i=1;i!=n;i+=2)
    {
        sum=sum+(a[i-1]-a[i]);
    }
    cout<<"sum";
}

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;

int main()
{
    int n;
    while(cin>>n)
    {
        vector<int> v(n,0);
        for(int i=0;i<n;i++)
        {
            cin >> v[i];
        }
        int sum=0;
        for(int i=0;i<n;i += 2)
        {
            sum += v[i+1] -v[i];
        }
        cout << sum << endl;
    }
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n,x;
    int sum=0;
    vector<int>a(n);
    cin>>n;
    for(int i=0;i<n;i++)
    {
        cin>>x;
        a.push_back(x);

    }
    sort(a.begin(),a.end());
    for(int i=0;i<n;i+=2)
    {
        sum=a[i+1]-a[i];
    }
    cout<<sum;
    return 0;
}

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define INF 100000000000000000
#define pb push_back
#define mp make_pair
//#define MAXX 200000
//vector<ll> Primes; ll isprime[MAXX+2],Ar[MAXX+100];
//void sieve(){
//    Primes.push_back(2);isprime[2]=1;
//    for(ll i=2;i<=MAXX;i+=2) Ar[i]=1;
//    for(ll i=3;i<=MAXX;i+=2){ if(Ar[i]==0) { Primes.push_back(i); isprime[i]=1; for(ll j=i*i;j<=MAXX;j+= i*2) Ar[j]=1;}}
//}
//double mysqrt(ll N){
//    double high,low,mid; high=(double)N;low=0.0;for(ll i=1;i<=64;i++){ mid=(high+low)/2; if(mid*mid>N) high=mid; else low=mid;}
//    return mid;}
//ll mod(ll B,ll M){ll X=B%M; if(X>=0) return X; else return M+X;}
///cin.ignore();
ll max(ll a,ll b) {if(a>b) return a; else return b;} ll min(ll a,ll b) {if(a<b) return a; else return b;}
ll pow(ll B,ll P) { ll S=1; for(ll i=1;i<=P;i++) S=S*B; return S;} ll fx4[]={1,-1,0,0}; ll fy4[]={0,0,1,-1};

int A[20000],B[20000];

int main()
{
    ///use always ll instead of int
    //sieve();

    ll T,N,M,X,Y,W;

    cin>>N;

    for(int i=1;i<=N;i++) cin>>A[i];

    ll ans=0;

    ll loop=N/2;

    for(int i=1;i<=N;i++)
    {
        ll MIN=10000,pos=1;

        if(A[i]==-1) continue;

        for(int j=1;j<=N;j++)
        {
            if(i==j || A[j]==-1) continue;

            X=abs(A[i]-A[j]);

            if(X<MIN)
            {
                //cout<<i<<" "<<j<<" "<<X<<" "<<MIN<<endl;
                MIN=X;
                pos=j;
            }
        }

        //cout<<i<<" "<<pos<<endl;

        if(A[i]!=-1) ans+=(abs(A[i]-A[pos]));
        A[i]=-1;
        A[pos]=-1;
    }

    cout<<ans<<endl;

    //for(int i=1;i<=N;i++) cout<<A[i]<<endl;

    return 0;
}

#include <bits/stdc++.h>
using namespace std;

int
main ()
{

    int n;
    cin >> n;

    vector < int > numbers;
    int v;
    for (int i = 0; i < n; i++)
    {
        cin >> v;
        numbers.push_back (v);
    }

    sort (numbers.begin (), numbers.end ());
    reverse (numbers.begin (), numbers.end ());

    int sum = 0;

    for (int j = 0; j <= n; j += 2)
    {
        sum = sum + (numbers[j] - numbers[j + 1]);
    }

    cout << sum;

    return 0;
}

#include <bits/stdc++.h>

using namespace std;

int a[105];

int main()
{
    int n;
    cin >> n;
    for(int i = 0; i <n; ++i){
        cin >> a[i];
    }
    int nmb = 0;
    for(int i = 0; i < 100; ++i){
        for(int j = 0; j < n; ++j){
            for(int k = 0; k < n; ++k){
                if(k == j){
                    continue;
                }
                if(a[k] - a[j] == i){
                    a[k] = -1;
                    a[j] = -1;
                    nmb += i;
                }
            }
        }
    }

    cout << nmb << "\n";
    return 0;
}

#include <iostream>
#include <algorithm>
using namespace std;
int mas[3];
int main() {
    cin >> mas[0] >> mas[1] >> mas[2];
    sort(mas, mas + 3);
    cout << mas[2] - mas[0];
}

#include <bits/stdc++.h>
using namespace std;
int main(){
	int n;
	cin>>n;
	int habilidad[n];
	for(int i=0; i<n; i++){
		int temp;
		cin>>temp;
		habilidad[i]=temp;
	}
	//formar parejas
	int parejas[n];
	int menor;
	int indices=-1;
	int cont=0;
	bool ban=false;
	for(int y=0; y<n; y++){
		menor=100;
		indices=-1;
		ban=false;
		for(int i=0; i<n; i++){
			if(i!=y){
				if(abs(habilidad[y]-habilidad[i])<menor && parejas[i]!=1){
					menor=abs(habilidad[y]-habilidad[i]);
					indices=i;
					ban=true;
				}
			}
		}
		if(ban==true){
	  cont+=menor;
	  parejas[indices]=1;
     }
	  parejas[y]=1;
	}
	cout<<cont;
	return 0;
}

#include <iostream>
#include <algorithm>
using namespace std;
int main(){
    int n,a[1000];
    cin>>n;
    for(int i=0;i<n;i++)cin>>a[i];
    sort(a,a+n);
    cout<<(a[n-1]-a[0]+1)-n<<endl;
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
main()
{
    int n,i,k,x=0,p;
    cin>>n;
    int a[n];
    for(i=0;i<n;i++)
    {
        cin>>a[i];
    }
    sort(a,a+n);
    for(i=0;i<n;i++)
    {
        k=a[i]-a[i-1];
        if(x<k)
        {
            p=k;
        }
        x=k;
    }
    cout<<p<<endl;
}

#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for (int i=a; i<b; ++i)
#define per(i,a,b) for (int i=a; i>=b; --i)
#define Z(a) (int)(a).size()
#define all(i) (i).begin(),(i).end()
#define pb push_back
#define I first
#define II second
typedef vector<int> VI;
typedef long long ll;
typedef pair<int,int> PII;
typedef double db;
// head

int n,h; VI ipt;

int main() {
	scanf("%d",&n);
	rep(i,0,n) scanf("%d",&h), ipt.pb(h);
	sort(all(ipt));

	int mx=0;
	rep(i,1,n) mx=max(mx,ipt[i]-ipt[i-1]);
	printf("%d",mx);
}

#include<bits/stdc++.h>
using namespace std;
#define FOR(i,a,b) for(int i=a;i<=b;i++)
main()
{
    int a[105];
    int n;cin>>n;
    FOR(i,1,n) cin>>a[i];
    sort(a+1,a+n+1);
    int res;
    for(int i=1;i<=n;i++)
    {
        res+=a[i+1]-a[i];
    }
    cout<<res;
}

#include <iostream>
#include <cstdio>
#include <cmath>
#include <algorithm>
#include <vector>
#include <stack>
#include <queue>
#include <utility>
#include <cstring>
#include <string>
#include <set>
using namespace std;

#define mp make_pair
#define fi first
#define se second
#define pb push_back
#define sz size
#define INFMAX 10000000000
#define INFMIN 10000000000

const int maxn = 100;

int n,a[maxn];
long ans=0;

void Input()
{
    cin >> n;
    for (int i=1; i<=n; i++) cin >> a[i];
}

void Solve()
{
    sort(a+1,a+n+1);
    for (int i=1; i<=n; i+=2)
        if (a[i] == a[i+1]) continue; else ans += abs(a[i]-a[i+1]);
}

void Output()
{
    cout << ans;
}

int main()
{
    Input();
    Solve();
    Output();
    return 0;
}

#include <bits/stdc++.h>

using namespace std;
int main()
{
int i,n;
cin>>n;
int a[n];
for(i=0;i<n;i++)
{
cin>>a[i];
}
sort(a,a+n);int c;
for(i=0;i<n;i+=2)
{
c+=(a[i+1]-a[i]);
}
cout<<c;
}

#include <bits/stdc++.h>
using namespace std;
const int N = 1e5;
int a[N];
int main ()
{
    int n;
    cin >> n;
    int ans = 0;
    for (int i = 0; i < n; i++)
    {
        cin >> a[i];

    }
    sort (a,a+n);
    for (int i = 1; i < n; i++)
    {
        ans = ans + (a[i] - a[i-1]);
    }
    cout << ans << endl;

}

#include<iostream>
#include<math.h>
using namespace std;
int main(){
    int n,dif,diff,p=1000,sum=0,m;
    cin>>n;
    int a[n];
    for(int i=0;i<n;i++)
        cin>>a[i];

    for(int i=0;i<n;i++){
        p=1000;
        m=0;
        if(a[i]==0) continue;
        for(int j=0;j<n;j++){
            if(i!=j && a[j]!=1000000){
                dif=a[i]-a[j];
                diff=abs(dif);
                //cout<<diff<<endl;
                if(diff<=p){
                    p=diff;
                    m=j;
                }
                //cout<<"m:"<<m<<endl;
            }
        }
        a[m]=1000000;
        a[i]=1000000;
        if(p==1000) p=0;
        //cout<<"p:"<<p<<endl;
        sum+=p;
    }
    cout<<sum;
    return 0;
}

#include <bits/stdc++.h>
using namespace std;
int main(){
	int n;
	cin>>n;
	int habilidad[n];
	for(int i=0; i<n; i++){
		int temp;
		cin>>temp;
		habilidad[i]=temp;
	}
	//formar parejas
	int parejas[n];
	int menor;
	int indices=-1;
	int cont=0;
	bool ban=false;
	for(int y=0; y<n; y++){
		menor=100;
		indices=-1;
		ban=false;
		if(parejas[y]!=1){
		for(int i=0; i<n; i++){
			if(i!=y){
				if(abs(habilidad[y]-habilidad[i])<menor && parejas[i]!=1){
					menor=abs(habilidad[y]-habilidad[i]);
					indices=i;
					ban=true;
				}
			}
		}
	}
		if(ban==true){
	  cont+=menor;
	  parejas[indices]=1;
     }
	  parejas[y]=1;
	}
	cout<<cont;
	return 0;
}

#include<bits/stdc++.h>

using namespace std;

int main()
{
    long long int n,i,res1=0,res2=0;
    cin>>n;
    int arr[n];
    for(i=0;i<n;i++){
        cin>>arr[i];
        if((n/2)>i){
            res1=res1+arr[i];
        }else{
          res2=res2+arr[i];
        }
    }
    if(res1>res2){
        cout<<res1-res2<<endl;
    }else{
    cout<<res2-res1<<endl;
    }
    return 0;
}

#include <bits/stdc++.h>
using namespace std;
int main()
{
	int n , c;
	cin >> n;
	vector <int> a(n);
	for (int i = 0; i < n; i++)
	{
		cin >> a[i];
	}
		sort (a.begin() , a. end());
	for (int i = 0; i < n; i += 2)
	{
		c += a[i + 1] - a[i];
	}
	cout << c << endl;
}

// C++ program for implementation of Bubble sort
#include <bits/stdc++.h>
using namespace std;

void swap(int *xp, int *yp)
{
	int temp = *xp;
	*xp = *yp;
	*yp = temp;
}

// A function to implement bubble sort
void bubbleSort(int arr[], int n)
{
	int i, j;
	for (i = 0; i < n-1; i++)

	// Last i elements are already in place
	for (j = 0; j < n-i-1; j++)
		if (arr[j] > arr[j+1])
			swap(&arr[j], &arr[j+1]);
}

/* Function to print an array */
void printArray(int arr[], int size)
{
	int i,s=0;
	for (i = 0; i < size; i++)
		cout << arr[i] << " ";
	cout << endl;
	for(int j=0;j<size;j++)
	{
		s+=arr[j+1]-arr[j];
		j++;
	}
	cout<<s;
}

// Driver code
int main()
{
	int arr[20],n;
	cout<<"enter size..\n";
	cin>>n;
	cout<<"array is...\n";
	for(int i=0;i<n;i++)
	{
		cin>>arr[i];
	}
	//int n = sizeof(arr)/sizeof(arr[0]);
	bubbleSort(arr, n);
	cout<<"Sorted array: \n";
	printArray(arr, n);
	return 0;
}

// This code is contributed by rathbhupendra

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n,a,b,x,y,z,arr[102];
    cin>>n;
    for(int i=0;i<n;i++)
    {
        cin>>arr[i];
    }
    a=0;
    for(int j=0;j<n-1;j=j+2)
   {
       a=a+(arr[j+1]-(arr[j]));

   }

    cout<<a<<endl;
}

#include <iostream>
#include <vector>
#include <algorithm>
#include <utility>

using namespace std;
int main() {
    int n, m = 0;
    cin >> n;
    vector<int> mas(n);
    for (int i = 0; i < n; i++) {
        cin >> mas[i];
    }
    sort (mas.begin(), mas.end());
    for (int i = 0; i < n; i++) {
        cout << mas[i] << " ";
    }
    for (int i = 0; i < n - 1; i++) {
        if (mas[i] <= mas[i + 1]) {
            m = m + (mas[i + 1] - mas[i]);
            i++;
        }
    }
    cout << "\n" << m;
}

#include<bits/stdc++.h>
using namespace std;

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    vector<int> v;
    int n;
    cin>>n;
    for(int i=0;i<n;i++)
    {
        int in;
        cin>>n;
        v.push_back(in);
    }
    sort(v.begin(),v.end());
    int out;
    for(int i=0;i<n-1;i+=2)
    {
        out+=abs(v[i]+v[i+1]);
    }
    cout<<out;
    return 0;
}

#include <bits/stdc++.h>
using namespace std;

int main() {
	int ilestudentow, wynik;
	cin >> ilestudentow;
	int skills[ilestudentow+2];
	for(int i=1; i<=ilestudentow; i++){
		cin >> skills[i];
	}
	sort(skills, (skills+1) + (ilestudentow+1));
	for(int i = 1; i<ilestudentow;){
	if(skills[i]==skills[i+1]){
		 i=i+2;
	}
	else {
		wynik=wynik+(skills[i+1]-skills[i]);
		 i=i+2;
	}}
	cout << wynik;
	return 0;
}

#include<bits/stdc++.h>
using namespace std;
int main()
{
    ios::sync_with_stdio(false);
    int n;
    cin>>n;
    int ans=0;
    int a[n];
    for(int i=0;i<n;i++)
    {
        cin>>a[i];
    }
    sort (a,a+n);
    int v=n/2;
    for(int i=0;i<n;i++)
    {
        if(a[i]!=a[i+1] &&v>=0)
           {
               ans+=a[i+1]-a[i];
               i+=2;
               v--;

           }
           i++;

    }
    return cout<<ans<<endl,0;
}

#include <iostream>
#include <cmath>
#include <iomanip>
using namespace std;

int main() {

	int n = 0;
	cin >> n;
	int *m;
	m = new int[n];
	for (int i = 0; i < n; i++) {
		cin >> m[i];
	}
	int d = 0, c = 0, k = 0, p = 0;
	int t = 0;

	for (int i = 0; i < n - 1; i++) {
		t = m[i];
		if (n == 2) {
			cout << abs(m[i] - m[i+1]);
			return 0;
		}
		for (int j = i + 1; j < n; j++) {
			if (m[j] == t) {
				m[j] = -100;
				m[i] = -100;
				continue;
			}
		}
		for (int j = i + 1; j < n; j++) {
			if ((m[i] == -100) || (m[j] == -100) || (m[j + 1] == -100)) {
				continue;
			}
			d = abs(m[i] - m[j]);
			k = abs(m[i] - m[j + 1]);
			if (d < k) {
				p = d;
			}
			else {
				p = k;
			}
		}
		c += p;
		p = 0;

	}
	cout << c;
	return 0;

}

#include <iostream>
#include<vector>
using namespace std;
int main() {
	// your code goes here
	int n,min,x,pair;
	pair=0;
	int arr[100];
	int ctr=0;
	cin>>n;
	for(int i=0;i<n;i++)
	{
	    cin>>arr[i];
	}
	for(int i=0;i<n;i++)
	{   min=100;
	    if(arr[i]!=0)
	        {
	    for(int j=0;j<n;j++)
	    {   if((j!=i)&&(arr[j]!=0))
	        {
	            x=abs(arr[j]-arr[i]);
	        if(x<min)
	        {
	            min=x;
	            pair=j;
	        }
	        }
	    }
	    arr[i]=0;
	    arr[pair]=0;
	    ctr=ctr+min;

	}
	}
	cout<<ctr;
	return 0;
}

#include <iostream>
#include<vector>
#include<string>
using namespace std;
int partition(vector<int> &values, int left, int right) {
    int pivotIndex = left + (right - left) / 2;
    int pivotValue = values[pivotIndex];
    int i = left, j = right;
    int temp;
    while(i <= j) {
        while(values[i] < pivotValue) {
            i++;
        }
        while(values[j] > pivotValue) {
            j--;
        }
        if(i <= j) {
            temp = values[i];
            values[i] = values[j];
            values[j] = temp;
            i++;
            j--;
        }
    }
    return i;
}

void quicksort(vector<int> &values, int left, int right) {
    if(left < right) {
        int pivotIndex = partition(values, left, right);
        quicksort(values, left, pivotIndex - 1);
        quicksort(values, pivotIndex, right);
    }
}

int main()
{
    int n;
    cin>>n;
    vector<int>t;
    for(int i=0;i<n;i++)
    {
        int temp;
        cin>>temp;
        t.push_back(temp);
    }

    int count=0;
    for(int i=0;i<t.size()-1;)
    {
        int temp=t[i+1]-t[i];
        count=count+temp;
        i=i+2;
    }
    cout<<count;
    return 0;
}

#include <iostream>
#include <cmath>
#include <string>
using namespace std;
int main()
{
    int n,d,min=10000,c=0;
    cin >> n;
    int a[n];
     for(int i=0;i<n;i++) {
         cin >> a[i];
     }
    for(int i=0;i<n;i++) {
        min=10000;
        for(int j=0;j<n;j++) {
            d=abs(a[i]-a[j]);
            if(d<min && i!=j) {
                min=d;
            }
        } c=c+min;
        }
        cout << c/2;
        return 0;

}

#include <stdio.h>
#include <math.h>

int main()
{
    int n;
    scanf("%d",&n);
    int a[n];
    for(int i=0;i<n;i++){
        scanf("%d",&a[i]);
    }
    int sum=0;
    for(int i=0;i<n/2;i++){
        long long  int temp=10000000000;
        for(int j=0;j<n;j++){
            if(i==j){
                continue;
            }
            if(fabs(a[i]-a[j])<=temp){
                temp=fabs(a[i]-a[j]);
            }
        }
        sum=sum+temp;
    }
    printf("%d\n",sum);
    return 0;
}

#include<bits/stdc++.h>
#define ll long long
using namespace std;
int main()

{
    ll t , n ;
    cin>>t;
    while(t--)
    {
        cin>>n;
        vector<ll> arr(n,0);
        for(int i =0;i<n;i++)
        cin>>arr[i];
        ll ans = 0;
        sort(arr.begin(),arr.end());
        for(int i=1;i<n;i=i+2)
        {
            ans += arr[i]-arr[i-1];
        }
        cout<<ans<<endl;
    }
    return 0;
}

#include <bits/stdc++.h>

using namespace std;

int main()
{
    int a[105],i,sum=0,n,k,c,b;
    cin>>n;
    for(i=1; i<=n; i++)
    {
        cin>>a[i];
    }
    sort(a,a+n+1);
    for(i=1; i<=n; i++)
    {
        sum+=a[i+1]-a[i];
        i++;}
        cout<<sum<<' ';

}

#include<bits/stdc++.h>

using namespace std;
int main()
{
    int  n,s[100],i;
    cin>>n;
    for(i=0;i<n;i++)
    {
        cin>>s[i];
    }
    sort (s,s+100);

    return 0;
}

//   ALLAH IS THE ALMIGHTY   //
#include<bits/stdc++.h>
using namespace std;
int main(){
  ios::sync_with_stdio(false);
  cin.tie(0);cout.tie(0);

  int n;
  cin >> n;
  int x, a(0), b(0), div = n / 2;;
  for (int i = 0; i < n; i++) {
    cin >> x;
    div > i ? a += x : b += x;
  }
  cout << b - a << '\n';
  return 0;
}
//           SOLVED!            //

#include <bits/stdc++.h>
using namespace std;

        int n,a[101],c;
      int main ()
        {
            cin>>n;

            for ( int i=0 ; i<n ; i++ )
               cin>>a[i];

            sort(a,a+n);

            for ( int i=0 ; i<n ; i+=2 )
            {
                if ( (a[i]==a[i+1]) || (a[i]==a[i-1]) )
                    continue;
            else
                        c+=(a[i+1]-a[i]);
            }

               cout<<c<<endl;

        return 0;

        }

#include <bits/stdc++.h>

using namespace std;

int a[105];

int main()
{
    int n;
    cin >> n;
    for(int i = 0; i <n; ++i){
        cin >> a[i];
    }
    int nmb = 0;
    for(int i = 0; i < 100; ++i){
        for(int j = 0; j < n; ++j){
            for(int k = 0; k < n; ++k){
                if(k == j){
                    continue;
                }
                if(abs(a[j] - a[k]) == i){
                    a[k] = -1;
                    a[j] = -1;
                    nmb += i;
                }
            }
        }
    }

    cout << nmb << "\n";
    return 0;
}

#include <bits/stdc++.h>

using namespace std;

int a[105];

int main()
{
    int n;
    cin >> n;
    for(int i = 0; i <n; ++i){
        cin >> a[i];
    }
    int nmb = 0;
    for(int i = 0; i < 100; ++i){
        for(int j = 0; j < n; ++j){
            for(int k = 0; k < n; ++k){
                if(k == j){
                    continue;
                }
                if(a[k] - a[j] == i){
                    a[k] = -1;
                    a[j] = -1;
                    nmb += i;
                }
            }
        }
    }

    cout << nmb << "\n";
    return 0;
}

#include <iostream>
#include<vector>
using namespace std;
int main() {
	// your code goes here
	int n,min,x,pair;
	pair=0;
	int arr[100];
	int ctr=0;
	cin>>n;
	for(int i=0;i<n;i++)
	{
	    cin>>arr[i];
	}
	for(int i=0;i<n;i++)
	{   min=abs(arr[i]-arr[i+1]);
	    for(int j=0;j<n;j++)
	    {   if((j!=i)&&(arr[j]!=0))
	        x=abs(arr[j]-arr[i]);
	        if(x<min)
	        {
	            min=x;
	            pair=j;
	        }
	    }
	    arr[i]=0;
	    arr[pair]=0;
	    ctr=ctr+min;

	}
	cout<<ctr;
	return 0;
}

#include<bits/stdc++.h>
#define ll long long
#define r(i,n) for(ll i=0;i<n;i++)
#define rp(i,a,b) for(ll i=a;i<b;i++)
#define rt return
#define db double
#define vd void
#define p(x) cout<<(x)<<endl;
#define ce continue;
#define bl bool
#define r0 rt 0;
#define r1 rt 1;
#define elif else if
#define bk break;
#define A p("A")
#define B p("B")
#define C p("C")
#define D p("D")
#define E p("E")
#define Sort(a) sort(a.begin(),a.end());
#define Reverse(a) reverse(a.begin(),a.end());
#define kaigyo cout<<endl;
#define pb(x) push_back(x);
using namespace std;
void Cond(int g){if(g)p("YES")else p("NO")rt;}
void cond(int g){if(g)p("Yes")else p("No")rt;}
ll power(ll k){ll t=1;r(i,k+1)t*=2;rt t;}
ll comb(ll i,ll j){ll up=1;for(ll n=i;n>i-j;n--){up*=n;}ll down=1;for(ll r=j;r>=1;r--)down*=r;rt up/(down);}//nCr.
ll gcd(ll a,ll b){if(a<b)swap(a,b);if(a%b==0)rt b;gcd(b,a%b);}
ll Digits(ll k){ll t=0;while(k){t+=k%10;k/=10;}rt t;}
char m1[26]={'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
char m2[26]={'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
char m3[10]={'0','1','2','3','4','5','6','7','8','9'};
const ll INF=(ll)1e18;
const ll MAX=(ll)1e5+10;
const ll NIL=-1;
struct Node{ll p,l,r;};
typedef struct edge{ll to,cost;}EDGE;
typedef pair<ll,ll> P;
#define ldb long double
ll ans=0,ct=0,ct1=0,ct2=0,cnt=0,tmp=0,g=0,n=0,m=0;
ll tmp1=0,tmp2=0,tmp3=0,tmp4=0,sum=0,pos=0,k=0;
ll len=0,len1=0,len2=0,len3=0,len4=0,len5=0;
ll mx=-INF,mn=INF;ll x;
map<ll,ll>mp,mp1,mp2;
set<P>st,st1,st2;
const ll MOD=((ll)1e9+7);

int main(){
cin>>n;
vector<ll>a(n);
r(i,n)cin>>a[i];
ans=0;
Sort(a)
k=n;ll s,t;
while(k){mn=INF;
	r(i,n){
		r(j,n){
	if(i==j||mp[i]||mp[j])ce
		if(abs(a[i]-a[j])<=mn){mn=abs(a[i]-a[j]);s=i;t=j;}
		}
	}
	//if(mn==INF)cout<<s<<" "<<t<<endl;
//	else p(mn)
ans+=(mn==INF)?0:mn;mp[s]=mp[t]=1;
k--;
}

p(ans)
	r0

}//main

#include <iostream>
#include <bits/stdc++.h>
using namespace std;
int main()
{
	int n,total;
	cin>>n;
	int a[n];
	for(int i=0;i<n;i++)
		cin>>a[i];
	sort(a,a+n);
	for(int j=0;j<n;j=j+2)
		total+=a[j+1]-a[j];
	cout<<total<<endl;
	return 0;
 }

#include <bits/stdc++.h>
#define    fast       ios::sync_with_stdio(false);cin.tie(0);cout.tie(0)
using namespace std;
inline int Int()
{
    int x;
    scanf("%d", &x);
    return x;
}
#define    Int        Int()
vector<int> v;
set<int> s;
int main()
{

    fast;
    int t=Int;
    int arr[t];
    for(int i = 0;i<t;i++)
        arr[i] = Int;

    sort(arr,arr+t);

    int cnt = 0;
    int sum = 0;
    for(int i = t/2 - 1;i>=0;--i){
        cnt += abs(arr[i] - arr[i+1]);
        sum +=  cnt;
    }
    cout << sum << endl;
}

#include<bits/stdc++.h>
using namespace std;
int main()
{
  int n;
  cin>>n;
  int s[n];
  int count=0;
  vector<int >v(101);
  for(int a=0;a<n;a++)
  {
    cin>>s[a];
    v[s[a]]++;
    if(v[s[a]]==2) count++;
  }
  //cout<<count;
  sort(s,s+n);
//  for(int a=0;a<n;a++) cout<<s[a]<<" ";
  int ans=0;
  if(count>=(n/2)) cout<<0<<endl;
  else
  {
    for(int a=1;a<n;a++)
    {
      if(s[a]==s[a-1])
       {
        s[a]=-1;
        s[a-1]=-1;
      }
      else if(s[a-1]!=-1)
      {
        ans+=abs(s[a]-s[a-1]);
      //  a=a+1;
        s[a]=-1;
        count++;
      }
      if(count>=(n/2)) break;
    }
    cout<<ans;
  }
  return 0;
}
/*#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
int main()
{
  ll t;
  cin>>t;
  while(t--)
  {
    ll n,k;
    cin>>n>>k;
    string s="abcdefghijklmnopqrstuvwxyz";
    ll l=n/k;
    for(ll a=0;a<k;a++)
    {
      for(ll b=0;b<l;b++)
      {
        cout<<s[a];
      }
    }
    if(n%k!=0)
    {
      cout<<s[k-1];
    }
  }
  return 0;
}*/

#include <iostream>

using namespace std;

long long n,i,j,k,l,a[1000001],ans,ans1;

int main() {
    cin >> n;
    for(i = 1; i <= n; i++) cin >> a[i];
    for(i = 1; i <= n / 2; i++) ans += a[i];
    for(i = n / 2 + 1; i <= n; i++) ans1+= a[i];
    cout << max(ans,ans1) - min(ans,ans1);
    return 0;
}

#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
const int N=105;
int data[N];
int n,sum;
int main()
{
	ios::sync_with_stdio(false);cin.tie(0);
	cin>>n;
	for(int i=0;i<n;i++) scanf("%d",&data[i]);
	sort(data,data+n);
	for(int i=0;i<n;i+=2) sum+=data[i+1]-data[i];
	cout<<sum<<'\n';
	return 0;
}

#include<iostream>
#include <algorithm>
using namespace std;
int main()
{
    int n,i,sum=0;
    cin>>n;
    int a[n];
    for(i=0;i<n;i++)
    cin>>a[i];
    sort(a,a+n);
    for(i=0;i<n;i++)
    {
        sum=sum+a[i]-a[i+1];
        i++;
    }
    cout<<sum;
}

#include<bits/stdc++.h>
using namespace std;

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    vector<int> v;
    int n;
    cin>>n;
    for(int i=0;i<n;i++)
    {
        int in;
        cin>>in;
        v.push_back(in);
    }
    sort(v.begin(),v.end());
    int out;
    for(int i=0;i<n-1;i+=2)
    {
        out+=abs(v[i]-v[i+1]);
    }
    cout<<out;
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
typedef vector<int> vi;
typedef vector< vector<int> > vii;
typedef vector<string> vs;
typedef unordered_map<int, int> uii;
typedef unordered_map<char, int> uci;
typedef unordered_map<string, int> usi;

int skillsDeterminer(vi skills) {
    vector < pair<int, int> > studentTeams;
    for(int i = 0; i < skills.size(); i++) {
        int currentPerson = skills[i];
        int diff = 1000;
        int secondPerson = 0;
        for(int j = 0; j < skills.size(); j++) {
            if(j!=i && skills[j]!=-1 && skills[i]!= -1) {
                int newDiff = abs(skills[i]-skills[j]);
                if(newDiff < diff) {
                    diff = newDiff;
                    secondPerson = j;
                }
            }
        }
        studentTeams.push_back(make_pair(currentPerson,skills[secondPerson]));
        skills[i] = -1;
        skills[secondPerson] = -1;
    }
    int minQues = 0;
    for(int i = 0; i < studentTeams.size(); i++) {
        if(studentTeams[i].first == -1 && studentTeams[i].second == -1) {
            continue;
        }
        else {
            int diff = abs(studentTeams[i].first - studentTeams[i].second);
            minQues += diff;
        }
    }

    // for (int i = 0; i < studentTeams.size(); i++)
    // {
    //     cout<<studentTeams[i].first<<" : "<<studentTeams[i].second<<endl;
    // }
    return minQues;

}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    //Insert your f**king code here
    int students;
    cin>>students;
    vi skills(students);
    for(int i = 0; i < students; i++) {
        cin>>skills[i];
    }
    int minSkills = skillsDeterminer(skills);
    cout<<minSkills;
    return 0;
}

#include<bits/stdc++.h>
#define ll long long
using namespace std;
int main()
{
    int n,sum=0;
    cin>>n;
    int a[n];
    for(int i=0;i<n;i++)
        cin>>a[i];
    //bubblesort;
    for(int i=0;i<n-1;i++)
    {
        for(int j=i;j<n-i-1;j++)
        {
            int t;
            if(a[j]>=a[j+1])
            {
                t=a[j];
                a[j]=a[j+1];
                a[j+1]=t;
            }
        }
    }
    for(int i=0;i<n;i+=2)
    {
        sum=sum+a[i+1]-a[i];
    }
    cout<<sum;
}

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n,x;
    int sum=0;
    vector<int>a(n);
    cin>>n;
    for(int i=0;i<n;i++)
    {
        cin>>x;
        a.push_back(x);

    }
    sort(a.begin(),a.end());
    for(int i=0;i<n;i+=2)
    {
        sum+=a[i+1]-a[i];
    }
    cout<<sum;
    return 0;
}

#include<bits/stdc++.h>

using namespace std;

int main()
{
    int n,sum1=0,sum2=0,i,tem;
    cin>>n;
    int arr[n];
    for(i=0;i<n;i++){
        cin>>arr[i];
    }
    for(i=0;i<n;i=i+2){
        sum1=sum1+arr[i];
    }
    for(i=1;i<n;i=i+2){
        sum2=sum2+arr[i];
    }
    tem=(n/2)-1;
    if(sum1>sum2){
       cout<<(sum1-sum2)+tem<<endl;
    }else{
    cout<<(sum2-sum1)+tem<<endl;
    }
    return 0;
}

#include<bits/stdc++.h>

using namespace std;

int main()
{
    int n,a,c=0;
    cin>>n;
    vector<int>v;
    for(int i=0;i<n;i++)
    {
        cin>>a;
        v.push_back(a);
    }
    sort(v.begin(),v.end());
    for(int i=0;i<=n-2;i++)
    {
        if(v[i]!=-1&&v[i]==v[i+1])
            {
                c++;
                v[i]=-1;
                v[i+1]=-1;
            }
    }
    if(c==n/2)
    {
        cout<<"0"<<endl;
        return 0;
    }
    int ans=0;
    for(int i=0;i<=n-2;i++)
    {
        if(v[i]!=-1&&v[i+1]!=-1)
        {
            ans+=abs(v[i+1]-v[i]);
            v[i]=-1;
            v[i+1]=-1;
        }
    }
cout<<ans<<endl;
return 0;
}

// ----- In the name of ALLAH, the Most Gracious, the Most Merciful -----

#include<bits/stdc++.h>
using namespace std;

#define sim template < class c
#define ris return * this
#define dor > debug & operator <<
#define eni(x) sim > typename \
  enable_if<sizeof dud<c>(0) x 1, debug&>::type operator<<(c i) {
sim > struct rge { c b, e; };
sim > rge<c> range(c i, c j) { return rge<c>{i, j}; }
sim > auto dud(c* x) -> decltype(cerr << *x, 0);
sim > char dud(...);
struct debug {
#ifdef LOCAL
~debug() { cerr << endl; }
eni(!=) cerr << boolalpha << i; ris; }
eni(==) ris << range(begin(i), end(i)); }
sim, class b dor(pair < b, c > d) {
  ris << "(" << d.first << ", " << d.second << ")";
}
sim dor(rge<c> d) {
  *this << "[";
  for (auto it = d.b; it != d.e; ++it)
    *this << ", " + 2 * (it == d.b) << *it;
  ris << "]";
}
#else
sim dor(const c&) { ris; }
#endif
};
#define deb(...) " [" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "

#define memo(a,val) memset(a,val,sizeof(a))
#define NINJA ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define all(a) a.begin(),a.end()
#define fo(i,n) for(int i=0;i<n;i++)
#define Fo(i,k,n) for(int i=k;i<n;i++)
#define for1(i,n) for(int i=1;i<=n;i++)
#define dloop(i,n) for(int i=n-1;i>=0;i--)
#define iii tuple<int,int,int>
#define vi vector<int>
#define ii pair<int,int>
#define vii vector<ii>
#define int long long
#define ld long double
#define pb push_back
#define endl "\n"
#define setbits __builtin_popcountll
#define mp map<int,int>
#define F first
#define S second
#define sz(v) (int)v.size()
#define mod 1000000007
#define inf (int)1e18

const int mxn = 110;
int a[mxn];
bool vis[mxn];

int32_t main(){
	NINJA;

	int n; cin >> n;
	for1(i,n) cin >> a[i];

	int cost = 0;

	for1(i,n){
		if(vis[i]) continue;
		int id = -1;
		int mn = inf;
		vis[i] = 1;
		for1(j,n){
			if(vis[j]) continue;
			if(mn > abs(a[i]-a[j])){
				mn = abs(a[i]-a[j]);
				id = j;
			}
		}
		// debug() << deb(mn) deb(id);
		vis[id] = 1;
		cost +=mn;
	}

	cout << cost << endl;

	return 0;
}

#include<bits/stdc++.h>
#define ll              long long
#define ull             unsigned long long
#define pb              push_back
#define fastread()      (ios_base:: sync_with_stdio(false),cin.tie(NULL));
using namespace std;
int main()
{
    fastread();
    int t,n,k;
    while(t--){
        cin>>n>>k;
        char a[] = {"abcdefghijklmnopqrstuvwxyz"};
        int j = 0;
        for(int i=0; i<n; i++){
            cout<<a[j++];
            if(j == k){
                j = 0;
            }
        }cout<<endl;
    }

    return 0;
}

#include <iostream>
#include <cmath>
#include <vector>
using namespace std;
int main ()
{
    int n;
    int value;
    int S=0;
    int minx =2147483647;
    cin>>n;
    vector<int>arr;
    for (int i =0 ;i<n ; i++)
    {
        cin>>value;
        arr.push_back(value);
    }
    int r;
    for (int i=0 ; i< arr.size() ;i++)
    {
        for (int j =i+1 ; j<arr.size(); j++)
        {
            //minx = min(minx,abs(arr[i]-arr[j]));
            if (minx > abs(arr[i] - arr[j]))
            {
                minx = abs(arr[i] - arr[j]);
                r = j;
            }
        }
        minx =2147483647;
        arr.erase(arr.begin() + r);
        S = S +abs(arr[i] - arr[r]);
    }
    cout<<S;
    return 0;
}

#include <bits/stdc++.h>

using namespace std;

int main(){
    int n;  cin >> n;
    vector<int> v(n);
    vector<tuple<int, int, int>> d;
    for(int i = 0; i < n; i++) cin >> v[i];
    sort(v.begin(), v.end());
    for(int i = 0; i < n; i++){
        for(int j = i+1; j < n; j++){
            d.push_back(make_tuple(abs(v[j] - v[i]), i, j));
        }
    }
    sort(d.begin(), d.end());
    int fkd[10000];
    memset(fkd, 0, sizeof(fkd));
    int ans = 0;
    int k = 0;
    for(int i = 0; k < n/2; i++){
        if(!fkd[get<1>(d[i])] and !fkd[get<2>(d[i])]){
            ans += get<0>(d[i]);
            fkd[get<1>(d[i])] = 1;
            fkd[get<2>(d[i])] = 1;
            k++;
        }
    }

    cout << ans;
}

#include<iostream>
#include<cmath>
#include<cstring>
#include<algorithm>
#include<cstdio>
using namespace std;
int m,n,i,j,k,sum;
int a[1000];
double pi[1000],f[100];
int main()
{
    freopen("input.txt","r",stdin);
    int n;
    scanf("%d",&n);
    for(i=1;n>=i;i++)
    {
        scanf("%d",&a[i]);
    }
    for(i=1,sum=0;n/2>=i;i++)
    {
        sum+=fabs(a[i]-a[n-i+1]);
    }
    printf("%d\n",sum);
    return 0;
}

#include<string.h>
#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
typedef long long ll;
int y[100000],z[2000000];
int main()
{
	int x;
	scanf("%d\n", &x);
	for (int i = 1; i <= x; i++)
    {
	scanf("%d", &y[i]);
	}
	sort(y, y + x + 1);
	for (int i = 1; i <= 2 * x; i++) {
		z[i] = y[i + 1] - y[i];
	}
	sort(z, z + 2 * x + 1); printf("%d\n", z[2 * x]);
	return 0;
}

#include<bits/stdc++.h>
using namespace std;

int n,a[100];
void BS()
{
    for(int i=1;i<=n-1;i++)
        for(int j=i+1;j<=n;j++)
            if(a[j]<a[i]) swap(a[j],a[i]);
}

main()
{
    cin>>n;
    for(int i=1;i<=n;i++) cin>>a[i];
    BS();
    int dem=0;
    for(int i=1;i<=n;i++) cout<<a[i]<<" ";
    for(int i=1;i<=n;i+=2)
        dem+=abs(a[i]-a[i+1]);
    cout<<dem;
}

    #include <bits/stdc++.h>
    using namespace std;

    #define SZ size()
    #define MIN LLONG_MIN
    #define MAX LLONG_MAX
    #define M 1000000007
    #define MP make_pair
    #define F first
    #define S second
    #define endl "\n"

    #define pb push_back
    #define N 100005

    typedef long long  ll;
    typedef unsigned long long ull;

    typedef vector<int> vi;
    typedef vector< vi > vvi;
    typedef vector<ll> vll;
    typedef vector<string> vs;
    typedef pair<int, int> pii;
    typedef map<int, int> mii;
    typedef map<char, int> mci;
    typedef map<string, int> msi;

    int main(){
        ios_base::sync_with_stdio(false);
        cin.tie(NULL);
        cout.tie(NULL);
    	// code part
    	int n; cin >>n; int a[N];
    	for(int i =0; i <n; i++) cin >>a[i];
    	sort(a, a+n);int s;
    	for(int i =0; i <n; i+=2) s+=a[i+1] - a[i];
    	cout << s<<endl;
    	return 0;
    }

#include<bits/stdc++.h>
#define ll long long
using namespace std;
int main()

{
    ll t , n ;
    cin>>t;
    while(t--)
    {
        cin>>n;
        vector<ll> arr(n,0);
        for(int i =0;i<n;i++)
        cin>>arr[i];
        ll ans = 0;
        sort(arr.begin(),arr.end());
        for(int i=1;i<n;i=i+2)
        {
            ans += arr[i]-arr[i-1];
        }
        cout<<ans<<endl;
    }
    return 0;
}

#include <bits/stdc++.h>
using namespace std;

int
main ()
{

    int n;
    cin >> n;

    vector < int > numbers;
    int v;
    for (int i = 0; i < n; i++)
    {
        cin >> v;
        numbers.push_back (v);
    }

    sort (numbers.begin (), numbers.end ());

    int sum = 0;
    int roznica = 0;

    for (int j = 0; j <= n; j += 2) {
        roznica = (numbers[j + 1] - numbers[j]);
        sum = sum + roznica;
    }

    cout << sum << " ";

    return 0;
}

#include<iostream>
#include<math.h>
using namespace std;
int main(){
    int n,dif,diff,p=1000,sum=0,m;
    cin>>n;
    int a[n];
    for(int i=0;i<n;i++)
        cin>>a[i];

    for(int i=0;i<n;i++){
        p=1000;
        m=0;
        for(int j=0;j<n;j++){
            if(i!=j && a[j]!=0){
                dif=a[i]-a[j];
                diff=abs(dif);
                //cout<<diff<<endl;
                if(diff<=p){
                    p=diff;
                    m=j;
                }
                //cout<<"m:"<<m<<endl;
            }
        }
        a[m]=0;
        a[i]=0;
        if(p==1000) p=0;
        //cout<<"p:"<<p<<endl;
        sum+=p;
    }
    cout<<sum;
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define n1 1000000
//#define fast ios_base::sync_with_stdio(false); cin.tie(NULL);
//fflush(stdout)
int main()
{
    //fast
ios_base::sync_with_stdio(false); cin.tie(NULL);
ll n;
cin>>n;
ll a[n1];
for(ll i=0;i<n;i++)
{
	cin>>a[i];
}
int ans=0;
for(int i=0;i<n;i++)
{
	//int n=a[i];
	for(int j=0;j<n;j++)
	{
		if(i!=j && a[i]==a[j])
		{
			a[i]=INT_MAX;
			a[j]=INT_MAX;
			break;
		}
	}
}
for(int i=0;i<n;i++)
{
	if(a[i]==INT_MAX)
	{
		continue;
	}
	int no=a[i];
	int index=0;
	int dif=INT_MAX;
	int k=i;
	for(int j=0;j<n;j++)
	{
		int c=abs(a[j]-no);
		if(j!=k &&  c<dif)
		{
			dif=c;
			index=j;
		}
	}
	a[i]=INT_MAX;
	a[index]=INT_MAX;
	//cout<<i<<" "<<index<<" "<<dif<<endl;
    ans+=dif;
}
cout<<ans<<endl;

return 0;
}

#include <iostream>
#include <algorithm>
using namespace std;
int mas[3];
int main() {
    cin >> mas[0] >> mas[1] >> mas[2];
    sort(mas, mas + 3);
    cout << mas[2] - mas[0];
}

#include<bits/stdc++.h>

using namespace std;

int main()
{
    int n;
    cin>>n;
    vector<int>v(n);
    for(int i=0;i<n;i++)
    {
        cin>>v[i];
    }
    sort(v.begin(),v.end());
    int count;
    for(auto it=v.begin();it<v.end();it=it+2)
    {
        count = count-(*it-*(it+1));
    }
    cout<<count;
}

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

int main() {

	int n;
	scanf("%d", &n);
	vector<int> v;
	int cur;
	for(int i=0; i<n; i++) {
		scanf("%d", &cur);
		v.push_back(cur);
	}
	sort(v.begin(), v.end());
	ll s;
	for(int i=0; i<v.size()-1; i+=2) {
		s += (v[i+1] - v[i]);
	}
	cout << s;

	return 0;
}

#include <bits/stdc++.h>
using namespace std;

int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);

	int t;
	cin>>t;
	while(t--){
		int n;
		cin>>n;
		if(n%2==0) cout<<n/2<<endl;
		else cout<<(n-3)/2+1<<endl;
	}
	return 0;
}

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;

int main()
{
    int n;
    while(cin>>n)
    {
        vector<int> v(n,0);
        for(int i=0;i<n;i++)
        {
            cin >> v[i];
        }
        int sum=0;
        for(int i=0;i<n;i += 2)
        {
            sum += v[i+1] -v[i];
        }
        cout << sum << endl;
    }
    return 0;
}

#include <bits/stdc++.h>
#include<algorithm>
#include<functional>
using namespace std;
int n,a[100001];
long long s;
int main()
{
    cin>>n;
    s=0;
    for (int i=1;i<=n;i+=2)
    {
        cin>>a[i];
        sort(a+1,a+n+1);
        s+=abs(a[i]-a[i+1]);
    }
    cout<<s;
}

#include<bits/stdc++.h>
#define mp make_pair
#define pb push_back
#define st first
#define nd second
typedef long long ll;
using namespace std;
ll X,N,T;
map<ll,ll> M;
main()
{
	ios_base::sync_with_stdio(NULL),cin.tie(0),cout.tie(0);
	cin>>N;
	for(;N--;T+=X*(1-M[X]),M[X]=1) cin>>X;
	if(T%2) cout<<T-M.begin()->first;
	else cout<<T;
}

#include <bits/stdc++.h>

using namespace std;

int main()
{
    int n, teams, problems = 0;;
    cin >> n;
    vector<int> student(n);
    for(int i = 0; i < n; i++) {
        cin >> student[i];
    }
    sort(student.begin(), student.end());
    for(int i = 0; i < n; i = i + 2) {
        problems = student[i + 1] - student[i];
    }
    cout << problems;
    return 0;
}

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main() {

	int x, y, sum = 0;
	vector <int> arr;

	cin >> x;

	while (x--) {

		cin >> y;
		arr.push_back(y);

	}

	sort(arr.begin(), arr.end(), greater<int>());

	for (int i = 0; i < arr.size(); i += 2) {

		cout << arr[i] << " " << arr[i + 1] << endl;

		sum += arr[i] - arr[i + 1];

	}

	cout << sum;

	return 0;
}