using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication3
{
    class Program
    {
        static void Main(string[] args)
        {
            long n = Convert.ToInt64(Console.ReadLine());
            if (n % 2 == 0)
                Console.WriteLine(n / 2);
            else
                Console.WriteLine(-(n + 1) / 2);
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {
            string input = Console.ReadLine();
            Int64 n=Int64.Parse(input);
            if (n % 2 == 0)
            {
                Console.WriteLine(n / 2);
            }
            else
            {
                Console.WriteLine(-1*(n / 2 + 1));
            }
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Code_Forces
{
    class Program
    {

        static void Main(string[] args)
        {
            long n = long.Parse(Console.ReadLine());
            if (n%2==0)
                Console.WriteLine(n/2);
            else
                Console.WriteLine(-(n/2+1));

        }
    }
}

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;

namespace codeforces
{
    class Program
    {
        // ★☆★☆★TYUPI☆★☆★☆
#if ONLINE_JUDGE
        private static readonly StreamReader reader = new StreamReader(Console.OpenStandardInput(1024 * 10), System.Text.Encoding.ASCII, false, 1024 * 10);
        private static readonly StreamWriter writer = new StreamWriter(Console.OpenStandardOutput(1024 * 10), System.Text.Encoding.ASCII, 1024 * 10);
#else
        private static readonly StreamWriter writer = new StreamWriter("output.txt");
        private static readonly StreamReader reader = new StreamReader("input.txt");
#endif

        static void Main(string[] args)
        {
            //   StreamReader objReader = new StreamReader("input.txt");
        //    reader = new StreamReader("input.txt");

            //int[] raod = Console.ReadLine().Split(' ').Select(x => int.Parse(x)).ToArray();
            long Rao =long.Parse( reader.ReadLine());

            if (Rao % 2 == 0)
            {

                writer.WriteLine(Rao/2);
                writer.Flush();
            }
            else
            {
                writer.WriteLine((Rao /2)-Rao);
                writer.Flush();
            }
        }
    }
}

using System;

namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
            long ans = 0;
            long a = Convert.ToInt64(Console.ReadLine());
            ans -= a / 2;
            if (a % 2 == 0)
            {
                ans *= -1;
            }
            else {
                ans -= 1;
            }
            Console.WriteLine(ans);
            //Console.ReadKey();
        }
    }
}

using System;
using System.Linq;

namespace _486A
{
    class Program
    {
        static void Main()
        {
               var n = long.Parse(Console.ReadLine());
               Console.WriteLine(n % 2 == 0 ? n / 2 : -(n + 1) / 2);
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace TestPlace
{
    class Program
    {
        static void Main(string[] args)
        {
            var value = Convert.ToInt64(Console.ReadLine());
            if(value%2==0)
                Console.WriteLine(value/2);
            else
                Console.WriteLine((value - 1)/2-value);
        }

    }
}

using System;
using System.Collections.Generic;
using System.Numerics;

namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {

            double n = double.Parse(Console.ReadLine());
            if (n%2==0)
            {
                Console.WriteLine(Math.Truncate(n/2));
            }
            else
            {
                Console.WriteLine(Math.Truncate(n/2)-n);
            }
        }
    }
}

using System;
using System.Linq;
using System.Collections.Generic;
public class Program
{
    static void Main(string[] args)
    {
        long N = long.Parse(Console.ReadLine());
        if (N % 2 == 0)
        {
            Console.WriteLine(N / 2);
        }
        else
        {
            Console.WriteLine((N - 1) / 2 - N);
        }
    }
}

using System;
using System.Text;

namespace CF_277
{
	class A_277
	{
		static void Main(string[] args)
		{
			//string[] ss = Console.ReadLine().Split(new char[]{' '}, StringSplitOptions.RemoveEmptyEntries);
			//int a = int.Parse(ss[0]);
			//int b = int.Parse(ss[1]);
			//string[] ss = Console.ReadLine().Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
			long n = long.Parse(Console.ReadLine());
			long sign = n % 2 == 0 ? 1 : -1;
			long mod = (n + 1) / 2;
			long ret = sign * mod;
			Console.WriteLine(ret);

//			Console.ReadKey();
		}
	}
}

using System;
class DELETEME
{
    static void Main()
    {
        var n = Int64.Parse(Console.ReadLine());
        var count = n / 2 + n % 2;
        var a = (1 + (count - 1)) * count;
        var b = (2 + (n - count - 1)) * (n - count);
        Console.WriteLine(b - a);
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp1
{
	class Program
	{
		static void Main(string[] args)
		{

			long n = Convert.ToInt64(Console.ReadLine());

			if (n % 2 == 0) Console.WriteLine(n / 2);

			else Console.WriteLine((-(n + 1) / 2));

		}
	}
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace AA
{
    class Program
    {
        static void Main(string[] args)
        {
            String a;
            a = Console.ReadLine();
            Int64 b = Convert.ToInt64(a);
            if (b % 2 != 0)
                Console.Write('-');
            Console.WriteLine(b / 2 + b % 2);
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace CodeForces
{
    public class Test
    {
        public static void Main()
        {
            long n = Convert.ToInt64(Console.ReadLine());
            if (n % 2 == 0)
            {
                Console.WriteLine(n/2);
            }
            else
            {

                Console.WriteLine(-n/2-1);
            }

        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Codeforces
{
    class Class32
    {
        public static void Main()
        {
            long a = long.Parse(Console.ReadLine());
            long f = 0;
            if (a % 2 == 1)
                f = -((a + 1) / 2);
            else
                f = a / 2;
            Console.WriteLine(f);
        }
    }
}

using System;

namespace CF_Function {
    class Program {
        static void Main(string[] args) {
            long input = Int64.Parse(Console.ReadLine());
            if(input % 2 == 0) {
                Console.WriteLine(input / 2);
                return;
            }
            Console.WriteLine(-(input + 1) /2);
        }
    }
}

using System;

namespace codeforces
{
    class Program
    {

        static void Main(string[] args)
        {
            //string[] str = Console.ReadLine().Split();
            long number = long.Parse(Console.ReadLine());
            long find = 0;

            if (number % 2 != 0)
                find = -(number / 2 + 1);
            else find = number / 2;

            Console.WriteLine(find);

        }
    }
}

using System;

namespace ACalculatingFunction
{
    class Program
    {
        public static long Func(long number)
        {
            if (number % 2 == 1)
            {
                return -(number + 1) / 2;
            }
            else
            {
                return number / 2;
            }
        }

        static void Main(string[] args)
        {
            var number = long.Parse(Console.ReadLine());
            Console.WriteLine(Func(number));
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Int64 n = Int64.Parse(Console.ReadLine()),nE,nO;
            nE = n / 2;
            nO = (n % 2 == 0) ? n/2 : (n/2)+1;
            Console.WriteLine(( nE * (nE + 1))  - (nO*nO));
        }
    }
}

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Net.NetworkInformation;

namespace ConsoleApp2
{
    public class Solution
    {
        static void Main(string[] args)
        {
            long n = long.Parse(Console.ReadLine());

            Console.WriteLine(n % 2 == 0 ? n / 2 : -(n / 2 + 1));
        }
    }
}

using System;
using System.Linq;
using System.Collections.Generic;
class Program
{
  public static void Main(string[] args)
  {
    long inp = Convert.ToInt64(Console.ReadLine());
    if(inp%2==0)
      Console.WriteLine(inp/2);
      else
      Console.WriteLine(-inp/2 - 1);
  }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace CalculatingFunction
{
    class Program
    {
        static void Main(string[] args)
        {

            long a = Convert.ToInt64(Console.ReadLine());
            long suma;
            if (a % 2 == 0)
            {
                long b = Convert.ToInt64(a / 2);
                suma = b * (b + 1) - (b * b);
            }
            else
            {
                long b = Convert.ToInt64((a + 1) / 2);
                suma = (b - 1) * b - (b * b);
            }
            Console.WriteLine(suma);
        }
    }
}

using System;

namespace resh
{
	class Program
	{
		public static void Main()
		{
			long n=long.Parse(Console.ReadLine());
			long f=0;
            if (n%2==0) f=n/2;
            else f=(n-1)/2-n;
            Console.Write(f);
		}
	}
}

using System;

namespace _486A
{
	class Program
	{
		static void Main(string[] args)
		{
			ulong n = ulong.Parse(Console.ReadLine());
			Console.WriteLine(n % 2 == 0 ? (n / 2).ToString() : "-" + ((n + 1) / 2).ToString());
		}
	}
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace FunctionCalculation
{
    class Program
    {
        static void Main(string[] args)
        {
            double n = double.Parse(Console.ReadLine());

            double result = 0;

            if (Func(n) > 0)
            {
                result = n / 2;
            }
            else
            {
                result = ((n - 1) / 2) - n;
            }

            //double result = 0.25 * (2 * Math.Pow(-1, n) * n + Math.Pow(-1, n) - 1);

            Console.WriteLine(result);
        }

        static double Func(double n)
        {
            return Math.Pow(-1, n) * n;
        }
    }
}

using System;

class Zada4ki
{
    static void Main()
    {
        long n = Convert.ToInt64(Console.ReadLine());
        long f = 0;
        if (n % 2 == 0) f = n / 2;
        else f = (n - 1) / 2 - n;
        Console.WriteLine(f);
    }
}

using System;

namespace CFDay11
{
    class Program
    {
        static void Main(string[] args)

        {
           long n = long.Parse(Console.ReadLine());
            if(n%2==0)
                Console.WriteLine(n/2);
            else
                Console.WriteLine(-(n/2)-1);
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace shangool
{
    class Program
    {
        /*static int GetInt()
        {
            return Int32.Parse(Console.ReadLine());
        }

        static string[] GetArray()
        {
            return Console.ReadLine().Split(' ');
        }*/
        static void Main(string[] args)
        {
            Int64 n;
            n =Int64. Parse(Console.ReadLine());
            if (n % 2 == 0) Console.WriteLine(n / 2);
            else
            {
                n++;
                Console.WriteLine((n / 2)*-1);
            }
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace _489A_Calculating_Function
{
    class Program
    {
        static void Main(string[] args)
        {

            Int64 input = Int64.Parse(Console.ReadLine());

            if (input %2==0)
            {
                Console.WriteLine(input / 2);
            }
            else
            {
                Console.WriteLine((-input - 1) / 2);
            }

        }
    }
}

using System;

namespace Main
{
	class MainClass
	{
		public static void Main (string[] args)
		{
			long n = Convert.ToInt64 (Console.ReadLine ());
			long result = 0;
			if (n % 2 == 0) {
				result = n / 2;
			} else {
				result = -(n + 1) / 2;
			}
			Console.WriteLine (result);
		}
	}
}

using System;
using System.Linq;

namespace ConsoleApp5
{
    class Program
    {
        static void Main(string[] args)
        {
            long n = Convert.ToInt64(Console.ReadLine());
            long res = 0;
            if (n % 2 == 0)
                res = n / 2;
            else
                res = -(n + 1) / 2;
            Console.WriteLine(res);
        }
    }
}

using System;
using System.Linq;
using System.Collections.Generic;
using System.Collections;

public class Program
{
	public static void Main()
	{
		long n=long.Parse(Console.ReadLine());

		Console.WriteLine(n%2==0 ? n/2 : ((n+1)/2)*-1);
	}
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace CODING_C_SHARP
{
    class Program
    {
        static void Main(string[] args)
        {
            long n = long.Parse(Console.ReadLine());
            long sum = 0;
            if (n % 2 == 0)
            {
                long t = n / 2;
                long f = t - 1;
                sum = t * t + t - f * f - f - n / 2;
            }
            else
            {
                long t = n / 2;
                long f = (n - 1) / 2;
                sum = t * t + t - f * f - f - (n + 1) / 2;
            }
            Console.Write(sum);
            Console.ReadLine();
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;

namespace codeforces {
    class Program {
        static void Main(string[] args) {
            double number=double.Parse(Console.ReadLine());
            double answer=number%2==0?number/2:(number+1)/-2;
            Console.WriteLine(answer);
        }
    }
}

using System;
using System.Collections.Generic;
using System.Text;

namespace Calculating_Function
{
    //Interface
    interface ICalculating_Function
    {
        long CalculateSeries();
    }

    //Functional Class
    class SeriesCalculation : ICalculating_Function
    {
        public long Num { get; set; }

        public long CalculateSeries()
        {
            long res = 0;

            if (Num %  2 == 0)
            {
                res = Num / 2;
            }
            else
            {
                res = (Num / 2) + 1;
                res *= (-1);
            }
            return res;
        }
    }

    //Driver Class
    class Program
    {
        static void Main(string[] args)
        {
            SeriesCalculation cal = new SeriesCalculation();

            cal.Num = Convert.ToInt64(Console.ReadLine());
            Console.WriteLine(cal.CalculateSeries());

            /*long n = Int64.Parse(Console.ReadLine());
            long sum = 0;
            long sum = n / 2;

            sum -= (n % 2) * n;
            Console.WriteLine(sum);*/

        }
    }
}

using System;

namespace Calculating_Function
{
    class Program
    {
        static void Main(string[] args)
        {
            long n = long.Parse(Console.ReadLine());
            if (n % 2 == 0)
            {
                Console.WriteLine(n/2);
            }
            else
            {
                Console.WriteLine(((n-1)/2)+(n*-1));
            }
        }
    }
}

using System;
using System.Collections.Generic;
namespace Olymp
{
    public class Program
    {
        static void Z1A ()
        {
            uint n, m, a;
            string str = Console.ReadLine ();
            string [] strs = str.Split (' ');
            n = UInt32.Parse (strs [0]);
            m = UInt32.Parse (strs [1]);
            a = UInt32.Parse (strs [2]);

            uint nn = n / a;
            if (n % a > 0)
                nn++;
            uint nm = m / a;
            if (m % a > 0)
                nm++;
            ulong result = (ulong)nn * (ulong)nm;
            Console.WriteLine (result);
        }

        static void Z4A ()
        {
            int w = Int32.Parse (Console.ReadLine ());
            if (w % 2 == 0 && w > 2)
                Console.WriteLine ("YES");
            else
                Console.WriteLine ("NO");
        }

        static void Z158A ()
        {
            int n, k;
            string [] strs = Console.ReadLine ().Split (' ');
            n = Int32.Parse (strs [0]);
            k = Int32.Parse (strs [1]);
            strs = Console.ReadLine ().Split (' ');
            int max = 0;
            int i;
            for (i = 0; i < k; i++) {
                max = Int32.Parse (strs [i]);
                if (max == 0) {
                    Console.WriteLine (i);
                    return;
                }
            }
            int sum = k;
            for (; i < n; i++) {
                if (Int32.Parse (strs [i]) < max)
                    break;
                sum++;
            }
            Console.WriteLine (sum);
        }

        static void Z71A ()
        {
            int n = Int32.Parse (Console.ReadLine ());
            string str;
            for (int i = 0; i < n; i++) {
                str = Console.ReadLine ();
                if (str.Length > 10) {
                    Console.WriteLine (str [0] + (str.Length - 2).ToString () + str [str.Length - 1]);
                } else {
                    Console.WriteLine (str);
                }

            }
        }

        static void Z118A ()
        {
            string str = Console.ReadLine ();
            str = str.ToLower ();
            str = str.Replace ("a", "");
            str = str.Replace ("o", "");
            str = str.Replace ("y", "");
            str = str.Replace ("e", "");
            str = str.Replace ("u", "");
            str = str.Replace ("i", "");
            for (int i = 0; i < str.Length; i++) {
                Console.Write ("." + str [i]);
            }

        }

        static void Z50A ()
        {

            string   [] strs = Console.ReadLine ().Split (' ');
            int N = Int32.Parse (strs [0]);
            int M = Int32.Parse (strs [1]);
            int result = 0;
            result = (N / 2) * M;
            N %= 2;
            M /= 2;
            result += M * N;
            Console.WriteLine (result);

        }

        static void Z158B ()
        {
            int n = Int32.Parse (Console.ReadLine ());
            string[] strs = Console.ReadLine ().Split (' ');
            int[] com = new int[4];
            for (int i = 0; i < 4; i++) {
                com [i] = 0;
            }
            int temp = 0;
            for (int i = 0; i < n; i++) {
                temp = Int32.Parse (strs [i]);
                com [temp - 1]++;
            }
            int sum = com [3];
            temp = Math.Min (com [2], com [0]);
            com [2] -= temp;
            com [0] -= temp;
            sum += temp;
            sum += com [2];
            sum += com [1] / 2;
            com [1] %= 2;
            sum += com [1];
            com [0] -= com [1] * 2;
            if (com [0] > 0) {

                sum += com [0] / 4;
                com [0] %= 4;
                if (com [0] > 0)
                    sum++;
            }
            Console.WriteLine (sum);

        }

        static void Z231A ()
        {

            int n = Int32.Parse (Console.ReadLine ());
            string[] strs;
            int sum = 0;

            for (int i = 0; i < n; i++) {
                strs = Console.ReadLine ().Split (' ');
                if (Int32.Parse (strs [0]) + Int32.Parse (strs [1]) + Int32.Parse (strs [2]) > 1)
                    sum++;
            }
            Console.WriteLine (sum);
        }

        static void Z282A ()
        {

            int n = Int32.Parse (Console.ReadLine ());
            int x = 0;
            string str;
            for (int i = 0; i < n; i++) {
                str = Console.ReadLine ();
                str = str.Replace ("X", "");
                if (str == "++") {
                    x++;
                } else {
                    x--;
                }
            }
            Console.WriteLine (x);
        }

        static  void Z116A ()
        {

            int n = Int32.Parse (Console.ReadLine ());
            int a = 0, b = 0;
            int sum = 0;
            int max = 0;
            string [] strs;
            for (int i = 0; i < n; i++) {
                strs = Console.ReadLine ().Split (' ');
                a = Int32.Parse (strs [0]);
                b = Int32.Parse (strs [1]);
                sum -= a;
                sum += b;
                if (sum > max) {
                    max = sum;
                }
            }
            Console.WriteLine (max);
        }

        static void Z131A ()
        {
            bool caps = true;
            string str = Console.ReadLine ();
            char first = str [0];
            for (int i = 1; i < str.Length; i++) {
                if (str [i] < 'A' || str [i] > 'Z')
                    caps = false;
            }
            if (caps) {
                str = str.ToLower ();
                if (first >= 'a' && first <= 'z')
                    first = first.ToString ().ToUpper () [0];
                else
                    first = first.ToString ().ToLower () [0];
                str = first + str.Substring (1);

            }
            Console.WriteLine (str);
        }

        static void Z96A ()
        {
            string str = Console.ReadLine ();
            int n = 0;
            char ch = 'w';
            for (int i = 0; i < str.Length; i++) {
                if (ch == str [i])
                    n++;
                else {
                    if (n >= 7) {
                        Console.WriteLine ("YES");
                        return;
                    }
                    ch = str [i];
                    n = 1;
                }
            }
            if (n < 7)
                Console.WriteLine ("NO");
            else
                Console.WriteLine ("YES");
        }

        static void Z266A ()
        {

            string str = Console.ReadLine ();
            str = Console.ReadLine ();
            int n = 0;
            int m = 0;
            char ch = ' ';
            for (int i = 0; i < str.Length; i++) {
                if (ch == str [i])
                    n++;
                else {
                    m += n;
                    ch = str [i];
                    n = 0;
                }
            }
            m += n;
            Console.WriteLine (m);
        }

        static void Z133A ()
        {
            string str = Console.ReadLine ();
            for (int i = 0; i < str.Length; i++) {
                if (str [i] == 'H' || str [i] == 'Q' || str [i] == '9') {

                    Console.WriteLine ("YES");
                    return;
                }

            }
            Console.WriteLine ("NO");

        }

        static void Z112A ()
        {
            string str1 = Console.ReadLine ();
            str1 = str1.ToLower ();
            string str2 = Console.ReadLine ();
            str2 = str2.ToLower ();
            int n = String.Compare (str1, str2);
            if (n != 0)
                Console.WriteLine (n / Math.Abs (n));
            else
                Console.WriteLine (0);
        }

        static void Z339A ()
        {
            int [] ch = new int[3];
            for (int i = 0; i < 3; i++) {
                ch [i] = 0;
            }
            string str = Console.ReadLine ();
            bool flag = false;
            for (int i = 0; i < str.Length; i++) {
                if (flag)
                    i++;
                else
                    flag = true;
                ch [Int32.Parse (str [i].ToString ()) - 1]++;
            }
            int j = 0;
            flag = false;
            while (j<3) {
                ch [j]--;

                if (ch [j] >= 0) {
                    if (flag) {
                        Console.Write ("+");
                    } else
                        flag = true;
                    Console.Write (j + 1);
                } else
                    j++;
            }
        }

        static void Z281A ()
        {
            string str = Console.ReadLine ();
            string f = str [0].ToString ();
            f = f.ToUpper ();
            str = f [0] + str.Substring (1);
            Console.Write (str);
        }

        static void Z82A ()
        {
            string[] names = new    string[5];
            names [0] = "Sheldon";
            names [1] = "Leonard";
            names [2] = "Penny";
            names [3] = "Rajesh";
            names [4] = "Howard";
            int n = Int32.Parse (Console.ReadLine ());
            int m = 5;
            while (m<n) {
                n -= m;
                m *= 2;
            }
            m /= 5;
            int i = 0;
            while (m<n) {
                n -= m;
                i++;
            }
            Console.Write (names [i]);
        }

        static void Z160A ()
        {
            int n = Int32.Parse (Console.ReadLine ());
            string[] str = Console.ReadLine ().Split (' ');
            List<int> moneys = new List<int> ();
            int sum = 0;
            for (int i = 0; i < n; i++) {
                moneys.Add (Int32.Parse (str [i]));
                sum += moneys [i];
            }

            int[] armon = moneys.ToArray ();
            Array.Sort (armon);
            int blz = 0;
            int j = armon.Length - 1;
            int ni = 0;
            while (blz<=sum&&j>=0) {
                blz += armon [j];
                sum -= armon [j];
                j--;
                ni++;
            }
            Console.WriteLine (ni);
        }

        static void Z148A ()
        {
            int k=Int32.Parse(Console.ReadLine());
            int l=Int32.Parse(Console.ReadLine());
            int m=Int32.Parse(Console.ReadLine());
            int n=Int32.Parse(Console.ReadLine());
            int d=Int32.Parse(Console.ReadLine());
                int sum=0;

            for (int i = 1; i <= d; i++) {
                if(i%k==0||i%l==0||i%m==0||i%n==0)
                    sum++;
            }
            Console.WriteLine(sum);
        }
        static void Z236A ()
        {
            string str=Console.ReadLine();
            int n=0;
            string ne="";
            bool k;
            for (int i = 0; i < str.Length; i++) {
                k=false;
                for (int j = 0; j < ne.Length; j++) {
if (str[i]==ne[j]) {
                        k=true;
                    }
                }
                if (!k) {
                        ne+=str[i];
                        n++;
                    }
            }
            if (n%2==0) {
                Console.WriteLine("CHAT WITH HER!");
            }
            else {
                Console.WriteLine("IGNORE HIM!");
            }
        }
        static int gdc (int left,int right)
        {
            while (left>0&&right>0) {
                if (left>right) {
                    left%=right;
                }
                else
                    right%=left;
            }
            return left+right;
        }
        static void Z119A ()
        {
            string[]str=Console.ReadLine().Split(' ');
            int[] ab=new int[2];

            ab[0]=Int32.Parse(str[0]);
            ab[1]=Int32.Parse(str[1]);
            int n=Int32.Parse(str[2]);
            int i=0;
            int m;
            while (true) {
                if(n==0)
                {
                    Console.WriteLine((i+1)%2);
                    return;
                }
                m=gdc(ab[i],n);
                n-=m;
                i=(i+1)%2;

            }

        }
        static void Z110A ()
        {
            string str=Console.ReadLine();
            int n=0;
            for (int i = 0; i < str.Length; i++) {
                if (str[i]=='4'||str[i]=='7') {
                    n++;
                }
            }
            if (n==4||n==7) {
                Console.WriteLine("YES");
            }
            else {
                Console.WriteLine("NO");
            }
        }
        static void Z467A ()
        {
            int n=Int32.Parse(Console.ReadLine());
            int res=0;
            string [] strs;
            for (int i = 0; i < n; i++) {
                strs=Console.ReadLine().Split(' ');
                if (Int32.Parse(strs[1])-Int32.Parse(strs[0])>=2) {
                    res++;
                }
            }
            Console.WriteLine(res);
        }
        static void Z271A ()
        {
            int n=Int32.Parse(Console.ReadLine());
            int []ye=new int[4];
            n++;
            for (int i = 0; i < 4; i++) {
                ye[i]=n/1000;
                n%=1000;
                n*=10;
            }
            bool flag=true;
            while (flag) {
                    for (int i = 0; i < 4; i++) {
                for (int j = 0; j < i; j++) {
                    if(ye[i]==ye[j])
                        {
                        ye[i]++;

                            for (int k = i+1; k < 4; k++) {
                                ye[k]=0;
                            }
                            i--;
                        }
                }
            }
                flag=false;
                for (int i = 1; i < 4; i++) {
                    if(ye[i]==10)
                    {
                        ye[i]%=10;
                        ye[i-1]++;
                        flag=true;
                    }
                }
            }
            for (int i = 0; i < 4; i++) {
                Console.Write(ye[i]);
            }

        }
        static void Z58A ()
        {
            string str=Console.ReadLine();
            str.ToLower();
            string sstr="hello";
            int j=0;
            for (int i = 0; i < str.Length; i++) {
                if(sstr[j]==str[i])
                    j++;
                if (j==sstr.Length) {
                    Console.WriteLine("YES");
                    return;
                }
            }
            Console.WriteLine("NO");
        }
        static void Z472A ()
        {
            int n=Int32.Parse(Console.ReadLine());
            if (n%2==0) {
                Console.Write("4 ");
                Console.Write(n-4);
            }
            else {
                Console.Write("9 ");
                Console.Write(n-9);
            }
        }
        static void Z460A ()
        {
            int res=0;
            int days=0;
            string[] strs=Console.ReadLine().Split(' ');
            int nosk=Int32.Parse(strs[0]);
            int nd=Int32.Parse(strs[1]);
            while (nosk!=0) {
                days+=nosk;
                res+=nosk;
                nosk=0;
                nosk=days/nd;
                days%=nd;
            }
            Console.Write(res);
        }
        static void Z379A ()
        {
            string[] strs=Console.ReadLine().Split(' ');
            int a=Int32.Parse(strs[0]);
            int b=Int32.Parse(strs[1]);
            int ogaroks=0;
            int h=0;
            while (a!=0) {
                h+=a;
                ogaroks+=a;
                a=ogaroks/b;
                ogaroks%=b;
            }
            Console.WriteLine(h);
        }
        static bool IsLucky (int n)
        {
            while (n>0) {
                int m=n%10;
                if (m!=4&&m!=7) {
                    return false;
                }
                n/=10;
            }
            return true;
        }
        static void Z122A ()
        {
            int n=Int32.Parse(Console.ReadLine());
            for (int i = 2; i <= n; i++) {
                if (n%i==0&&IsLucky(i)) {
                    Console.WriteLine("YES");
                    return;
                }
            }
            Console.WriteLine("NO");
        }
        static void Z136A ()
        {
            int n=Int32.Parse(Console.ReadLine());
            int[] pod=new int[n];
            string[] strs=Console.ReadLine().Split(' ');
            for (int i = 0; i < n; i++) {
                pod[Int32.Parse(strs[i])-1]=i+1;
            }
            for (int i = 0; i < n; i++) {
                Console.Write(pod[i].ToString()+" ");
            }
        }
        static void Z228A ()
        {
            string[]strs=Console.ReadLine().Split(' ');
            List<int> n=new List<int>();
            for (int i = 0; i < 4; i++) {
                bool flag=true;
                for (int j = 0; j < n.Count; j++) {
                    if(Int32.Parse(strs[i])==n[j])
                    {
                        flag=false;
                        break;
                    }
                }
                if (flag) {
                    n.Add(Int32.Parse(strs[i]));
                }
            }
            Console.WriteLine(4-n.Count);
        }
        static void Z263A ()
        {
            string[]strs;
            int x=0,y=0;
            for (int i = 0; i < 5; i++) {
                strs=Console.ReadLine().Split(' ');
                for (int j = 0; j < 5; j++) {
                    if (strs[j]=="1") {
                        x=j+1;
                        y=i+1;
                    }
                }

            }
            Console.WriteLine((Math.Abs(3-x)+Math.Abs(3-y)));
        }
        static void Z266B ()
        {
            string[]strs=Console.ReadLine().Split(' ');
            int n=Int32.Parse(strs[0]);
            int t=Int32.Parse(strs[1]);
            string str=Console.ReadLine();
            char[] chs=new char[str.Length];
            for (int i = 0; i < str.Length; i++) {
                chs[i]=str[i];
            }
            for (int i = 0; i < t; i++) {
                int j=0;
                while(j+1<n)
                {
                    if (chs[j]=='B'&&chs[j+1]=='G') {
                        char ch=chs[j];
                        chs[j]=chs[j+1];
                        chs[j+1]=ch;
                        j+=2;
                    }
                    else {
                        j++;
                    }
                }
            }
            for (int i = 0; i < chs.Length; i++) {
            Console.Write(chs[i]);
            }

        }
        static void Z41A ()
        {
            string str1=Console.ReadLine();
            string str2=Console.ReadLine();
            if (str1.Length!=str2.Length) {
                Console.WriteLine("NO");
                return;
            }
            for (int i = 0; i < str1.Length; i++) {
                if (str1[i]!=str2[str2.Length-i-1]) {

                Console.WriteLine("NO");
                return;
                }
            }
            Console.WriteLine("YES");
        }
        static void Z144A ()
        {
            int n=Int32.Parse(Console.ReadLine());
            string[]strs=Console.ReadLine().Split(' ');
            int[] rost=new int[n];
            int max=0;
            int min=n-1;
            for (int i = 0; i < n; i++) {
                rost[i]=Int32.Parse(strs[i]);
                if(rost[i]>rost[max])
                    max=i;
            }
            int sum=0;
            while (max!=0) {
                int temp=rost[max];
                rost[max]=rost[max-1];
                rost[max-1]=temp;
                sum++;
                max--;
            }

            for (int i = n-1; i >=0; i--) {

                if (rost[i]<rost[min]) {
                    min=i;
                }
            }
            while (min!=rost.Length-1) {
                int temp=rost[min];
                rost[min]=rost[min+1];
                rost[min+1]=temp;
                sum++;
                min++;
            }
            Console.WriteLine(sum);
        }
        static void Z451A ()
        {
            string[] names=new string[2];
            names[0]="Akshat";
            names[1]="Malvika";
            string[] strs=Console.ReadLine().Split(' ');
            int n=Int32.Parse(strs[0]);
            int m=Int32.Parse(strs[1]);
            n=Math.Min(n,m)-1;
            n%=2;
            Console.WriteLine(names[n]);

        }
        static void Z344A ()
        {
            int n=Int32.Parse(Console.ReadLine());
            int ostr=1;
            string str=Console.ReadLine();
            char ch=str[1];
            for (int i = 1; i < n; i++) {
                str=Console.ReadLine();
                if (ch==str[0]) {
                    ostr++;
                }
                ch=str[1];
            }
            Console.WriteLine(ostr);
        }
        static void Z486A ()
        {
            long n=Int64.Parse(Console.ReadLine());
            long sum=n/2;
            sum-=(n%2)*n;
            Console.WriteLine(sum);
        }
        public static void Main ()
        {
            Z486A ();
        }

    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Collections;

namespace ConsoleApp3
{
    class Program
    {
        static void Main(string[] args)
        {
            long n = Convert.ToInt64(Console.ReadLine());
            //long f = 0;
            if (n % 2 == 0)
            {
                Console.WriteLine(n / 2);
            }
            else
            {
                Console.WriteLine(-((n / 2) + 1));
            }
            //Console.ReadKey();
        }
    }
}

using System;
using System.Text;
using System.Collections.Generic;
class Problem
{
    static void Main()
    {
        long n = Convert.ToInt64( Console.ReadLine() );

        Console.WriteLine( n % 2 == 0 ? n / 2 : -n / 2 - 1 );
    }
}

using System;
using System.Collections.Generic;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            long n = Convert.ToInt64(Console.ReadLine());
            int sign = -1;
            if (n % 2 == 0)
            {
                Console.WriteLine(n / 2);
            }
            else
            {
                Console.WriteLine(((n / 2) + 1) * sign);
            }
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ChallengeCalculatingFunction
{
    class Program
    {
        static void Main(string[] args)
        {
            var n = long.Parse(Console.ReadLine());

            var value = n/2;
            if (n % 2 == 0)
            {
                Console.WriteLine(value);
            }
            else
            {
                Console.WriteLine(-value-1);
            }
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace CodeForcesTest.Round277Div2
{
    public class CalculatingFunction
    {
        public static void Main()
        {
            string line = Console.ReadLine();
            long input = Convert.ToInt64(line);

            long a = 0;
            if (input%2 == 0)
            {
                a = input/2;
            }
            else
            {
                a = (input + 1)/-2;
            }
            Console.WriteLine(a);
        }
    }
}

using System;

namespace _486A_Function
{
    class Program
    {
        static void Main(string[] args)
        {
            long n = long.Parse(Console.ReadLine());

            double func = 0;

         if( n % 2 == 0)
                {
                    func =  (n + 1) / 2;
                }
         else
                {
                    func += Math.Floor((-n) / 2.0);
                }

            Console.WriteLine(func);
        }
    }
}

using System;

namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
            var n = double.Parse(Console.ReadLine());
            double d = Math.Ceiling(n/ 2);
            d = n % 2 == 0 ? d * 1 : d * -1;

            Console.WriteLine(d);
        }
    }
}

using System;

class Program
{
    static void Main()
    {
        long n = long.Parse(Console.ReadLine());
        Console.WriteLine((long)(n/2)+n%2*Math.Pow(-1,n%2)*n);
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using System.Text.RegularExpressions;

class Program
{
    static public int[] readIntArray()
    {
        return (from string s in Console.ReadLine().Split(' ') select Convert.ToInt32(s)).ToArray();
    }

    static public long[] readLongArray()
    {
        return (from string s in Console.ReadLine().Split(' ') select Convert.ToInt64(s)).ToArray();
    }
    static public ulong[] readULongArray()
    {
        return (from string s in Console.ReadLine().Split(' ') select Convert.ToUInt64(s)).ToArray();
    }
    public static int readInt()
    {
        return Convert.ToInt32(Console.ReadLine());
    }
    public static long readLong()
    {
        return Convert.ToInt64(Console.ReadLine());
    }

    static void Main(string[] args)
    {
        long n = readLong();
        if (n % 2L == 0)
        {
            Console.WriteLine(n/2);
        }
        else
        {
            Console.WriteLine((n-1)/2 - n);
        }

    }

}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Numerics;

namespace Codility
{
    class Program
    {
        public static BigInteger codeforce(BigInteger a)
        {
            if (a % 2 == 0)
                return a / 2;
            BigInteger x = a / 2 + 1;
            return 0 - x;
        }

        static void Main(string[] args)
        {
            var a = Console.ReadLine().Split().Select(BigInteger.Parse).ToArray()[0];
            //var b = Console.ReadLine().Split().Select(int.Parse).ToArray()[0];
            //var c = Console.ReadLine().Split().Select(int.Parse).ToArray()[0];
            //var arr = Console.ReadLine().Split().Select(long.Parse).ToArray();
            Console.WriteLine(codeforce(a));
            //Console.WriteLine(solution1(-1, 3, 3, 1));
            //Console.WriteLine(solution("banana"));

            Console.ReadLine();
        }
    }
}

using System;
using System.IO;
using System.Linq;

class Program
{
    static char[] SPACE = new[] { ' ' };

    static void Main(string[] args)
    {
#if DEBUG
        using (var input = new StreamReader("input.txt"))
        using (var output = new StreamWriter("output.txt"))
        {
            Console.SetIn(input);
            Console.SetOut(output);

            int n = 0;
            do
            {
                Console.WriteLine();
                Console.WriteLine("Sample {0}", ++n);
                Prog();
            } while (Console.ReadLine() == string.Empty);
        }
#else
            Prog();
#endif
    }

    static int __ptr = 0;
    static string[] __input;
    static int NextInt()
    {
        return int.Parse(__input[__ptr++]);
    }
    static long NextLong()
    {
        return long.Parse(__input[__ptr++]);
    }
    static void ReadTokens(int n)
    {
        __ptr = 0;
        __input = Console.ReadLine().Split(SPACE, n);
    }

    //

    static void Prog()
    {
        ReadTokens(1);
        long n = NextLong();

        if (n % 2 == 1)
            Console.WriteLine(-((n + 1) / 2));
        else
            Console.WriteLine(n / 2);
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication33
{
    class Program
    {
        static void Main(string[] args)
        {
            long value = long.Parse(Console.ReadLine());

            if (value % 2 == 0)
            {
                Console.WriteLine(value / 2);
            }
            else
            {
                Console.WriteLine(value / 2 - value);

            }
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace t_prime
{
    class Program
    {
        static void Main(string[] args)
        {
            long n = long.Parse(Console.ReadLine());

                if (n%2==0)
                {
                    Console.WriteLine(n/2);
                }
                else
                {
                    Console.WriteLine(((n/2)+(n%2))*-1);
                }
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Text.RegularExpressions;
using System.IO;

namespace ConsoleApplication5
{
    class Program
    {
        static void Main(string[] args)
        {
            Int64 n = Int64.Parse(Console.ReadLine());
            //string[] pelnai = Console.ReadLine().Split(' ');
            if (n % 2 == 0)
            {
                Console.WriteLine(n / 2);
            }
            else
            {
                Console.WriteLine("-" + Math.Ceiling((double)n / 2));
            }
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication33
{
    class Program
    {
        static void Main(string[] args)
        {
            long n = long.Parse(Console.ReadLine());
            double res = 0;
            long power = 1;

                if (n % 2 == 0)
                {
                    Console.WriteLine(n / 2);

                }
                else
                {
                    Console.WriteLine(n / 2 - n);

                }

            Console.Read();
        }
    }
}

using System;
using System.Collections.Generic;
using System.IO;

namespace prA {

    class Program {
#if ONLINE_JUDGE
        private static readonly StreamReader reader = new StreamReader(Console.OpenStandardInput(1024 * 10), System.Text.Encoding.ASCII, false, 1024 * 10);
        private static readonly StreamWriter writer = new StreamWriter(Console.OpenStandardOutput(1024 * 10), System.Text.Encoding.ASCII, 1024 * 10);
#else
        private static readonly StreamWriter writer = new StreamWriter("output");
        private static readonly StreamReader reader = new StreamReader("input");
#endif
        static void Main(string[] args) {
            long p = long.Parse(reader.ReadLine());
            long ans = p / 2;
            if(p % 2 == 1)
                ans -= p;
            writer.WriteLine(ans);

            writer.Flush();
#if !ONLINE_JUDGE
            writer.Close();
#endif
        }
        private static int Next() {
            int c;
            int res = 0;
            do {
                c = reader.Read();
                if(c == -1)
                    return res;
            } while(c != '-' && (c < '0' || c > '9'));
            int sign = 1;
            if(c == '-') {
                sign = -1;
                c = reader.Read();
            }
            res = c - '0';
            while(true) {
                c = reader.Read();
                if(c < '0' || c > '9')
                    return res * sign;
                res *= 10;
                res += c - '0';
            }
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication9
{
    class Program
    {
        static void Main(string[] args)
        {
            long n = long.Parse(Console.ReadLine());
            double sum;
            sum = Math.Ceiling(Convert.ToDouble(n)/2);
            if (n % 2 != 0)
                sum *= -1;
            Console.WriteLine(sum);
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Codeforces
{
    class Program
    {
        private static long n;

        static void Main( string[] args )
        {
            n = init();
            Console.WriteLine(calculationFunction(n));
            //Console.ReadLine();

        }

        static long init()
        {
            return long.Parse( Console.ReadLine() );
        }

        static long calculationFunction( long n )
        {
            if ( (n % 2) == 1 )
            {
                return -1 - (n - 1) / 2;
            }
            else return n / 2;
        }

    }

}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace YOLO
{
    class Program
    {
        static void Main(string[] args)
        {
            long n;
            n = Convert.ToInt64(Console.ReadLine());
            if(n%2==0){
                Console.Write(n/2);
            }
            else{
                Console.Write(-((n/2)+1));
            }
        }
    }
}

using System;

namespace Codeforces
{
  class Program
  {
    static void Main(string[] args)
    {
      Int64 n = Int64.Parse(Console.ReadLine());

      Int64 r = (Int64)Math.Pow(-1, n) * (Int64) Math.Ceiling(n / 2.0) ;

      Console.WriteLine(r);
    }
  }
}

using System;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            string v_vod = Console.ReadLine();
            Int64 n = Int64.Parse(v_vod);
            if (n % 2 == 0)
            {
                Console.WriteLine(n / 2);
            }
            else
            {
                Console.WriteLine((n - 1) / 2 - n);
            }
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            ulong n = Convert.ToUInt64(Console.ReadLine());
            if(n%2==0)
            {
                //-1    1   -2  2   -3  3   -4  4
                Console.Write(n / 2);
            } else
            {
                Console.Write("-" + (n / 2 + 1));
            }
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
//using System.Text;
//using System.Threading.Tasks;

namespace Problem486A {
    class Program {
        static void Main(string[] args) {
            long n = Convert.ToInt64(Console.ReadLine());
            if (n % 2 == 0) {
                long result = n / 2;
                Console.WriteLine(result);
            } else {
                long result = -(n + 1) / 2;
                Console.WriteLine(result);
            }
        }
    }
}

using System;
using System.IO;
using System.Linq;
using System.Collections.Generic;

namespace Test1
{
	class MainClass
	{
		public static void Main (string[] args)
		{

			long n = long.Parse (Console.ReadLine());
			if (n % 2 == 0)
				Console.Write (n / 2);
			else
				Console.Write (n / (-2) - 1);
		}
	}
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace CalculatingFunction
{
    class Program
    {
        static void Main(string[] args)
        {
            long n = long.Parse(Console.ReadLine());
            if (n % 2 == 0)
                Console.WriteLine(n / 2);
            else
                Console.WriteLine((n - 1) / 2 - n);

        }
    }
}

using System;

static class Solution
{
    public static void Main(string[] args)
    {
        ulong n = ulong.Parse(Console.ReadLine());

        if(n % 2 == 1)
            Console.Write('-');

        Console.WriteLine((n + 1) / 2);
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication52
{
    class Program
    {
        static void Main(string[] args)
        {
            Int64 n = Int64.Parse(Console.ReadLine());
            Int64 summ;
            if(n%2 ==1)
                summ = ((n - 1)/ 2) * (1 + n)/2  - ((n + 1)/ 2) * (1 + n)/2 ;

            else
                  summ = n * (2 + n) / 4 - n * (1 + n-1) / 4;

            Console.WriteLine(summ);

        }
    }
}

using System;

namespace _468A
{
    class Program
    {
        static void Main(string[] args)
        {
            long n = long.Parse(Console.ReadLine());

            long floorHalf = (long)(n/2);
            long res = floorHalf * (floorHalf + 1) - (n - floorHalf)*(n - floorHalf);

            Console.WriteLine("{0}", res);
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace CF_486A
{
    class Program
    {
        static void Main(string[] args)
        {
            long n = long.Parse(Console.ReadLine());

            Console.WriteLine(n%2 == 0 ? n/2 : -(n + 1)/2);
        }
    }
}

using System;
using System.IO;

namespace CF277
{
    class Program
    {
        static void Main(string[] args)
        {
            Solution(Console.In, Console.Out);
        }

        static void Solution(TextReader sr, TextWriter sw)
        {
            long n = Int64.Parse(sr.ReadLine());
            if (n == 2)
            {
                sw.WriteLine(1);
                return;
            }
            var result = (long) Math.Ceiling((double)n/2);
            sw.WriteLine(n % 2 == 0 ? result : -result);
        }
    }
}

using System;

namespace def
{
    public static class Program
    {
        public static void Main()
        {
            var line = Console.ReadLine();
            var a = long.Parse(line);
            long sum;
            if (a%2 == 0)
                sum = a/2;
            else
                sum = -a/2 - 1;
            Console.WriteLine(sum);
        }
    }
}

using System;
class App
{
        static void Main()
        {
                long num = Convert.ToInt64(Console.ReadLine()), ans;
                if(num % 2 == 0)
                        ans = num / 2;
                else
                        ans = -(num + 1) / 2;
                Console.WriteLine(ans);
        }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace _486A_Calculating_Function
{
    class Program
    {
        static void Main(string[] args)
        {
            Decimal n = Convert.ToDecimal(Console.ReadLine());

            if (n % 2 == 0)
            {
                Console.WriteLine(n / 2);
            }

            else
            {
                Console.WriteLine(-((n + 1) / 2));
            }
        }
    }
}

using System;

namespace A._Calculating_Function
{
    class Program
    {
        static void Main(string[] args)
        {
            var number = Convert.ToInt64(Console.ReadLine());
            if (number % 2 == 0)
                Console.WriteLine(number / 2);
            else
                Console.WriteLine(-(number + 1) / 2);

        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

class program
{
    static void Main()
    {
        long n = long.Parse(Console.ReadLine()), m=n;
        Console.WriteLine(m-((n>>1)<<1) == 0 ? n>>1 : (n>>1)-m);
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace A.Подсчёт_функции
{
    class Program
    {
        static void Main(string[] args)
        {
            long n = long.Parse(Console.ReadLine());

            Console.WriteLine(fun(n));
            Console.ReadLine();
        }

        static long fun(long n)
        {
            if (n % 2 == 0)
                return n / 2;
            else
                return -n / 2 - 1;
        }
    }
}

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Diagnostics;

using System.Linq;

using System.Text;

using System.IO;
public class Test
{
	public static void Main()
	{
		long  n,x;
		string  a;
a=Console.ReadLine();
n=Convert.ToInt64(a);
		if(n%2==1)
		n=-(n+1)/2;
		else
		n=n/2;

		Console.Write(n);

	}
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace CodeForces
{
    class Program
    {
        static void Main(string[] args)
        {
            long number = long.Parse(Console.ReadLine());
            Console.WriteLine(number%2==0?number/2:Math.Floor(number/-2.0));
        }
    }
}

 using System;
    using System.Collections.Generic;
    using System.Globalization;
    using System.Linq;
    using System.Text;

    public class Program
    {
        public static void Main(string[] args)
        {
            long n = long.Parse(Console.ReadLine());
            long sumEven = 0;
            long sumOdd = 0;
            long sum = 0;
            sumOdd += (n * n) / 2;
            sumEven += (n * (n + 1)) / 2;
            if ((n % 2) == 0)
            {
                Console.WriteLine(sumEven - sumOdd);
            }
            else
            {
                Console.WriteLine(sumOdd - sumEven);
            }

        }
    }

using System;
    using System.Collections.Generic;
    using System.Globalization;
    using System.Linq;
    using System.Text;

    public class Program
    {
        public static void Main(string[] args)
        {
            var n = int.Parse(Console.ReadLine());
            var sumEven = 0;
            var sumOdd = 0;
            var sum = 0;
            sumOdd -= (n * n) / 2;
            sumEven += (n * (n + 1)) / 2;

            Console.WriteLine(sumOdd + sumEven);

        }
    }

using System;
    using System.Collections.Generic;
    using System.Globalization;
    using System.Linq;
    using System.Text;

    public class Program
    {
        public static void Main(string[] args)
        {
            long n = long.Parse(Console.ReadLine());
            long ano = 1 + ((n - 1) * 2);
            long ane = 2 + ((n - 1) * 2);
            long oddN = (n * (1 + ano)) / 2;
            long evenN = (n * (2 + ane)) / 2;
            long sum = 0;
            if ((n % 2) == 0)
            {
                sum = ((long)evenN - (long)oddN) / 2;
            }
            else
            {
                sum = ((long)oddN - (long)evenN) / 2;
            }

            Console.WriteLine(Math.Round((decimal)sum, MidpointRounding.AwayFromZero));

        }
    }

using System;
using System.IO;
using System.Linq;

class Program
{
    static char[] SPACE = new[] { ' ' };

    static void Main(string[] args)
    {
#if DEBUG
        using (var input = new StreamReader("input.txt"))
        using (var output = new StreamWriter("output.txt"))
        {
            Console.SetIn(input);
            Console.SetOut(output);

            int n = 0;
            do
            {
                Console.WriteLine();
                Console.WriteLine("Sample {0}", ++n);
                Prog();
            } while (Console.ReadLine() == string.Empty);
        }
#else
            Prog();
#endif
    }

    static int __ptr = 0;
    static string[] __input;
    static int NextInt()
    {
        return int.Parse(__input[__ptr++]);
    }
    static long NextLong()
    {
        return long.Parse(__input[__ptr++]);
    }
    static void ReadTokens(int n)
    {
        __ptr = 0;
        __input = Console.ReadLine().Split(SPACE, n);
    }

    //

    static void Prog()
    {
        ReadTokens(1);
        long a = NextLong();

        long r = (a + a % 2) / 2 * ((a % 2 == 0) ? -1 : 1);

        Console.WriteLine(r);
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace A.Calculating_Function
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());
            int i=n;
            int sum = 0;
            int f = 0;
            while (i >4)
            {
                i--;
                sum = sum + i;
            }
            if (n % 2 == 0)
            {
                 f = (-1 + 2 - 3 + sum + n);
            }
            else
            {
                 f = (-1 + 2 - 3 + sum + (-1*n));
            }
            Console.WriteLine(f);
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace A.Calculating_Function
{
    class Program
    {
        static void Main(string[] args)
        {
            long n = int.Parse(Console.ReadLine());
            long sum = 0;
            if (n%2 == 0 )
            {
                sum = n / 2;
            }
            else
            {
                sum = (n +1) / 2;
            }
            Console.WriteLine(sum);
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication52
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());
            Int64 summ;
            if(n%2 ==1)
                  summ = (n-1)*(2 + n-1)/4 - (n+1)*(1+n)/4;
            else
                  summ = n * (2 + n) / 4 - n * (1 + n-1) / 4;

            Console.WriteLine(summ);
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication52
{
    class Program
    {
        static void Main(string[] args)
        {
            Int64 n = Int64.Parse(Console.ReadLine());
            Int64 summ;
            if(n%2 ==1)
                  summ = (n-1)*(2 + n-1)/4 - (n+1)*(1+n)/4;
            else
                  summ = n * (2 + n) / 4 - n * (1 + n-1) / 4;

            Console.WriteLine(summ);

        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace CF_486A
{
    class Program
    {
        static void Main(string[] args)
        {
            long n = int.Parse(Console.ReadLine());

            Console.WriteLine(n%2 == 0 ? n : -(n + 1)/2);
        }
    }
}

using System;

class Program
{
    static void Main()
    {
        double n = double.Parse(Console.ReadLine());
        int res = 0;
        if(n%2==0)
        {
            res = (int)(n / 2);
        }
        else
        {
            res =-(int)( n / 2 + 1);
        }
        Console.WriteLine(res);
    }
}

using System;

class Program
{
    static void Main()
    {
        double n = double.Parse(Console.ReadLine());
        double res = 0;
        if(n%2==0)
        {
            res = n / 2;
        }
        else
        {
            res =-( n / 2 + 1);
        }
        Console.WriteLine(res);
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            long n = 0;
            n = Convert.ToInt32(Console.ReadLine());
            long s = 0;
            for (long i = 1; i < n + 1; i++) {
                s = s + i * ((-1) ^ i);
            }

            Console.WriteLine(s);
            Console.ReadLine();
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            long n = 0;
            n = Convert.ToInt32(Console.ReadLine());
            long s = 0;
            for (long i = 1; i < n + 1; i++) {
                s = s + i * (-1) ^ i;
            }

            Console.WriteLine(s);
            Console.ReadLine();
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            long n = 0;
            n = Convert.ToInt32(Console.ReadLine());
            long s = 0;
            long sum = 0;
            for (long i = 1; i < n + 1; i++) {
                if (i % 2 == 0) { s = i; }
                else { s = -i; }
                sum = sum + s;

            }

            Console.WriteLine(s);
            Console.ReadLine();
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Remoting.Metadata.W3cXsd2001;
using System.Text;
using System.Threading.Tasks;

namespace codeforces
{
    class Program
    {
        static void Main(string[] args)
        {
            string line = Console.ReadLine();
            double a = Double.Parse(line);
            double result = 0;
            if (a % 2 == 0)
            {
                result = a / 2;
            }
            else
            {
                result = ((a / 2) + 1) * -1;
            }
            Console.WriteLine(result);
            Console.ReadLine();
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace CalculatingFunction
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = 5;
            Console.WriteLine(n);
            Console.WriteLine(Funcion(n));
        }

        public static int Funcion(int a)
        {
            if (a == 1)
                return  -1;
            else
            {
                if (a % 2 == 0)
                    return Funcion(a - 1) + a;
                else
                    return  Funcion(a - 1) - a;
            }

        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace CalculatingFunction
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = 4;
            Console.WriteLine(Funcion(n));
        }

        public static int Funcion(int a)
        {
            if (a == 1)
                return  -1;
            else
            {
                if (a % 2 == 0)
                    return Funcion(a - 1) + a;
                else
                    return  Funcion(a - 1) - a;
            }

        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace CalculatingFunction
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine(Funcion(4));
            Console.WriteLine(Funcion(5));
        }

        public static int Funcion(int a)
        {
            if (a == 1)
                return  -1;
            else
            {
                if (a % 2 == 0)
                    return Funcion(a - 1) + a;
                else
                    return  Funcion(a - 1) - a;
            }

        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace CalculatingFunction
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = 4;
            Console.WriteLine(n);
            Console.WriteLine(Funcion(n));
        }

        public static int Funcion(int a)
        {
            if (a == 1)
                return  -1;
            else
            {
                if (a % 2 == 0)
                    return Funcion(a - 1) + a;
                else
                    return  Funcion(a - 1) - a;
            }

        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication10
{
    class Program
    {

        static void Main(string[] args)
        {
            ulong n = ulong.Parse(Console.ReadLine());
            if(n%2==0)
            {
                Console.WriteLine(n / 2);
            }
            else
            {
                Console.WriteLine("-" + (n / 2)+1);
            }

        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication10
{
    class Program
    {

        static void Main(string[] args)
        {
            ulong n = ulong.Parse(Console.ReadLine());
            if(n%2==0)
            {
                Console.WriteLine(n / 2);
            }
            else
            {
                Console.WriteLine("-" + n / 2);
            }

        }
    }
}

#region imports
using System;
using System.Globalization;
using System.IO;
using System.Linq;

#endregion

namespace CodeForces
{
    class Problem
    {
        const bool IsContest = true;

        long arithmSum1n(long n)
        {
            return (1 + n) * n / 2;
        }

        void Solve()
        {
            var n = _.NextLong();
            _.WriteLine(-arithmSum1n(n) + 4 * arithmSum1n(n / 2));
        }

        #region shit
        private readonly InOut _ = new InOut(IsContest);
        static void Main(string[] args)
        {
            var p = new Problem();
            p.Solve();
            p._.Close();
        }
    }
    class InOut
    {
        private const string InputFile = "input.txt";
        private const string OutputFile = "output.txt";
        public StreamWriter Cout { get; private set; }
        public StreamReader Cin { get; private set; }
        private void SetConsoleIo()
        {
            Cin = new StreamReader(new BufferedStream(Console.OpenStandardInput()));
            Cout = new StreamWriter(new BufferedStream(Console.OpenStandardOutput()));
        }
        private void SetFileIo(string inputFile, string outputFile) { Cin = new StreamReader(inputFile); Cout = new StreamWriter(outputFile); }
        public InOut() { SetConsoleIo(); }
        public InOut(string inputFile, string outputFile) { SetFileIo(inputFile, outputFile); }
        public InOut(bool isContest) { if (isContest) SetConsoleIo(); else SetFileIo(InputFile, OutputFile); }
        public void WriteLine(object x) { Cout.WriteLine(x); }
        public void Close() { Cin.Close(); Cout.Close(); }
        public void WriteLine(string format, params object[] args) { Cout.WriteLine(format, args); }
        private int _pos;
        private string[] _tokens;
        public string NextToken()
        {
            while (_tokens == null || _pos == _tokens.Length)
            {
                // ReSharper disable once PossibleNullReferenceException
                _tokens = Cin.ReadLine().Split(" \t".ToCharArray(), StringSplitOptions.RemoveEmptyEntries);
                _pos = 0;
            }
            return _tokens[_pos++];
        }
        public int NextInt() { return int.Parse(NextToken()); }
        public long NextLong() { return long.Parse(NextToken()); }
        public double NextDouble() { return double.Parse(NextToken(), CultureInfo.InvariantCulture); }

        #endregion
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication3
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());
            int[] a = new int[n];
            for (int i = 0; i < n; i++)
            {
                a[i] = a[i] + 1;
                if (a[i] % 2 != 0)
                    a[i] = -a[i];
            }

            int k = 0;
            for (int i = 0; i < n; i++)
            {
                k = k + a[i];
            }
            Console.WriteLine(k);
        }
    }
}

using System;

namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
            long ans = -2;
            long a = Convert.ToInt32(Console.ReadLine());
            for (int i = 4; i < a; i++) {
                ans += i;
            }
            if(a % 2 != 0)
            {
                a *= -1;
            }
            ans += a;
            Console.WriteLine(ans);
            //Console.ReadKey();
        }
    }
}

using System;

namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
            double ans = -2;
            int a = Convert.ToInt32(Console.ReadLine());
            for (int i = 4; i < a; i++) {
                ans += i;
            }
            ans += Math.Pow(Convert.ToDouble(-1), Convert.ToDouble(a)) * a;
            Console.WriteLine(1);
        }
    }
}

using System;

namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
            double ans = -2;
            int a = Convert.ToInt32(Console.ReadLine());
            for (int i = 4; i < a; i++) {
                ans += i;
            }
            ans += Math.Pow(Convert.ToDouble(-1), Convert.ToDouble(a)) * a;
            Console.WriteLine(ans);
        }
    }
}

using System;

namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
            long ans = 0;
            long a = Convert.ToInt32(Console.ReadLine());
            ans -= a / 2;
            if(a % 2 != 0)
            {
                a *= -1;
            }
            ans += a;
            Console.WriteLine(ans);
            //Console.ReadKey();
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            int input = 5;//Convert.ToInt32(Console.ReadLine());
            int result = 0;

            for (int i = 1; i <= input; i++)
            {
                if ((i & 1) == 1)
                    result += (i * -1);
                else
                    result += i;
            }

            Console.WriteLine(result);
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            int input = Convert.ToInt32(Console.ReadLine());
            int result = input / 2;

            if ((input & 1) == 0)
                result = (result + 1) * -1;
            Console.WriteLine(result);
        }
    }
}

using System;
using System.Linq;
using System.Collections.Generic;
public class Program
{
    static void Main(string[] args)
    {
        uint N = uint.Parse(Console.ReadLine());
        if (N % 2 == 0)
        {
            Console.WriteLine(N / 2);
        }
        else
        {
            Console.WriteLine((N - 1) / 2 - N);
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace CheckCable
{
    class Program
    {

        static void Main(string[] args)
        {
            CalculateFunction();
        }

        static void CalculateFunction()
        {
            long n = Convert.ToInt32(Console.ReadLine());
            long Fx = 0;

            if (n % 2 == 0)
                Fx = n / 2;
            else
                Fx = 0 - n / 2;
            Console.WriteLine(Fx);
        }
    }
}

using System;

namespace Issue_486A
{
    class Program
    {
        public static void Main(string[] args) {
            var num = ReadInt();

            var even = (num & 1) == 0;
            var fN = num / 2 + (even ? 0 : 1);

            fN = even ? fN : (~fN + 1);

            Console.WriteLine(fN);
        }

        private static bool IsInputError = false;

        private static int ReadInt() {
            const int zeroCode = (int) '0';

            var result = 0;
            var isNegative = false;
            var symbol = Console.Read();
            IsInputError = false;

            while (symbol == ' ') {
                symbol = Console.Read();
            }

            if (symbol == '-') {
                isNegative = true;
                symbol = Console.Read();
            }

            for ( ;
                (symbol != -1) && (symbol != ' ');
                symbol = Console.Read()
            ) {
                var digit = symbol - zeroCode;

                if (symbol == 13) {
                    break;
                }

                if (digit < 10 && digit >= 0) {
                    var cache1 = result << 1;
                    var cache2 = cache1 << 2;
                    result = cache1 + cache2 + digit;
                } else {
                    IsInputError = true;
                    break;
                }
            }

            return isNegative ? ~result + 1 : result;
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Coding
{

    class Program
    {

        static long SumOdds(long n)
        {
            long x = (long)(-1 * (Math.Pow(n, 2)));
            return x;
        }

        static long SumEven(long n)
        {
            long x = n * (n+1);

            return x;
        }
        static void Main(string[] args)
        {
            long result;
            long n = long.Parse(Console.ReadLine());

            if (n % 2 == 0)
                result = SumOdds(n / 2) + SumEven(n / 2);
            else
                result = SumOdds(n / 2 + 1) + SumEven(n / 2);

            Console.WriteLine(result);

        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Coding
{

    class Program
    {

        static long SumOdds(long n)
        {
            long x = (long)(-1 * (Math.Pow(n, 2)));
            return x;
        }

        static long SumEven(long n)
        {
            long x = n * (n+1);

            return x;
        }
        static void Main(string[] args)
        {
            long result;
            long n = long.Parse(Console.ReadLine());

            if (n % 2 == 0)
                result = SumOdds(n / 2) + SumEven(n / 2);
            else
            {
                decimal d = n;
                d = Math.Ceiling(d / 2);
                result = SumOdds((long)d) + SumEven(n / 2);
            }

            Console.WriteLine(result);

        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace calculation_function
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());

            double a;
            if (n % 2 == 0)
            {
                a = (-1 + (2 - 3) + Math.Pow(-1, n) * n);
                Console.WriteLine(a);
            }

            else
            {
                a = (-1 + (2 - 3) -( Math.Pow(-1, n) * n)-(n+1));
                Console.WriteLine(a);
            }
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace calculation_function
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());

            double a;
            if (n % 2 == 0)
            {
                a = (-1 + (2 - 3) + Math.Pow(-1, n) * n);
                Console.WriteLine(a);
            }

            else
            {
                a = (-1 + (2 - 3) +(n-1)+ ( Math.Pow(-1, n) * n));
                Console.WriteLine(a);
            }
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace calculation_function
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());

            double a=0;
            double c=0;
            if (n % 2 == 0)
            {
                a = (-1 + (2 - 3) + Math.Pow(-1, n) * n);
                Console.WriteLine(a);
            }

            else if(n>4)
            {

                for (int i = 1; i <= n; i++)
                {
                    a = 4 + (Math.Pow(-1, n) * n);
                }
                Console.WriteLine((-2+a));
            }
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            char[] Str = Console.ReadLine().ToCharArray();

            string Strok = "";
            int n = 0;
            bool answer = false;

            if (Str.Length > 8)
            {
                for (int i = 0; i < 8; i++)
                {
                    Strok = Strok + Str[i];
                }
                answer = true;
                n = Str.Length - 8;
            }
            else
            {
                Strok = new string(Str);
            }
            int value = Convert.ToInt32(Strok);

            if (value % 2 == 0)
                value = value / 2;
            else
                value = (-1) * (value + 1) / 2;

            Strok = value.ToString();

            for (int i = 0; i < n; i++)
                Strok = Strok + '0';

            Console.WriteLine(Strok);

        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Numerics;

namespace WarmingUpC_Sharp
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());
            Console.WriteLine(Math.Pow(-1, n) * (n + 1) / 2);
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace CF486A
{
    class Program
    {
        static void Main(string[] args)
        {
        }
    }
}

using System;
class Program
{
    static void Main()
    {
        Console.WriteLine(int.Parse(Console.ReadLine()) / 2);
    }
}

using System;

namespace CalculatingFunction
{
    class Program
    {
        static void Main(string[] args)
        {
            double n = Convert.ToDouble(Console.ReadLine());

            if (n % 2 == 0)
            {
                Console.WriteLine(n/2);
            }
            else
            {
                Console.WriteLine(-(n - n/2));

            }
        }
    }
}

using System;
using System.Collections.Generic;
using System.Numerics;

namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {

            double n = double.Parse(Console.ReadLine());
            if (n%2==0)
            {
                Console.WriteLine(n/2);
            }
            else
            {
                Console.WriteLine((n/2)-n);
            }
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp1
{
	class Program
	{
		static void Main(string[] args)
		{

			double n = Convert.ToInt32(Console.ReadLine());

			if (n % 2 == 0) Console.WriteLine(n - 2);
			else
			{
				Console.WriteLine(-n+2);
			}
		}
	}
}

using System;

namespace myApp {
    class Program {
        static void Main (string[] args) {
            int a = int.Parse(Console.ReadLine());
            Console.WriteLine((a / 2 + 1) * (-1 * a%2));
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace hamtinhtoan
{
    class Program
    {
        static void Main(string[] args)
        {
            long a=long.Parse(Console.ReadLine()),b=0;
            object s;
            if (a == 1) Console.WriteLine(-1);
            else
            {
                if (a % 2 == 0)
                {
                    b = a;
                    a -= 1;
                }
                else if (a % 2 == 1)
                {
                    b = a - 1;
                }
                s = (a + 1) * ((a - 1) / 2 + 1)/2 * (-1) + (b + 2) * ((b - 2) / 2 + 1)/2;
                Console.WriteLine(s);
            }

        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace hamtinhtoan
{
    class Program
    {
        static void Main(string[] args)
        {
            long a=long.Parse(Console.ReadLine()),b=0, s=0;
            if (a == 1) Console.WriteLine(-1);
            else
            {
                if (a % 2 == 0)
                {
                    b = a;
                    a -= 1;
                }
                else if (a % 2 == 1)
                {
                    b = a - 1;
                }
                s = (a + 1) * ((a - 1) / 2 + 1)/2 * (-1) + (b + 2) * ((b - 2) / 2 + 1)/2;
                Console.WriteLine(s);
            }

        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Code7.Tamrin
{
    class Program
    {
        static void Main(string[] args)
        {
            long n = Convert.ToInt64(Console.ReadLine());

            Console.WriteLine((n % 2 == 0)?n/2 : (-1) * (n / 2)+1) ;

        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Code7.Tamrin
{
    class Program
    {
        static void Main(string[] args)
        {
            long n = Convert.ToInt64(Console.ReadLine());

            Console.WriteLine((n % 2 == 0)?n/2 : (-1) * n / 2) ;

        }
    }
}

using System;
using System.Collections.Generic;

public class Test
{
	public static void Main()
	{
		long f = long.Parse(Console.ReadLine());

		if(f==1)
		{
			Console.WriteLine(-1);
		}
		if(f % 2 == 0)
		{
			Console.WriteLine(f/2);
		}
		else
		{
			Console.WriteLine((f+1)/2*(-1));

		}
	}
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

    class Program
    {
        static void Main(string[] args)
        {

            double  n=Convert.ToDouble(Console.ReadLine());
            if (n % 2 == 0)
            {
                n = n / 2;
            }
            else if (n % 2 != 0)
            {
                n = (n / 2) - n;
            }
            Console.Write(n);

        }
    }

using System;

namespace Calculating_Function
{
    class Program
    {
        static void Main(string[] args)
        {
            SeriesCalculation cal = new SeriesCalculation();

            cal.Num = Convert.ToInt32(Console.ReadLine());
            Console.WriteLine(cal.CalculateSeries());
        }
    }

    class SeriesCalculation : ICalculating_Function
    {
        public int Num { get; set; }

        public double CalculateSeries()
        {
            int eNum = 0;
            int oNum = 0;

            if (Num % 2 == 0)
            {
                eNum = Num / 2;
                oNum = Num / 2;
            }
            else
            {
                eNum = Num / 2;
                oNum = (Num / 2) + 1;
            }

            double oddNum = Math.Pow(oNum,2);
            double evNum = eNum * (eNum + 1);

            double res = evNum - oddNum;

            return res;
        }
    }

    interface ICalculating_Function
    {
        double CalculateSeries();
    }

}

using System;

namespace Calculating_Function
{
    //Driver Class
    class Program
    {
        static void Main(string[] args)
        {
            SeriesCalculation cal = new SeriesCalculation();

            cal.Num = Convert.ToInt64(Console.ReadLine());
            Console.WriteLine(cal.CalculateSeries());
        }
    }

    //Interface
    interface ICalculating_Function
    {
        double CalculateSeries();
    }

    //Main Functional Class
    class SeriesCalculation : ICalculating_Function
    {
        public double Num { get; set; }

        public double CalculateSeries()
        {
            double eNum = 0;
            double oNum = 0;

            if (Num % 2 == 0)
            {
                eNum = Num / 2;
                oNum = Num / 2;
            }
            else
            {
                eNum = Num / 2;
                oNum = (Num / 2) + 1;
            }

            double oddNum = Math.Pow(oNum,2);
            double evNum = eNum * (eNum + 1);

            double res = evNum - oddNum;

            return res;
        }
    }
}

using System;

namespace Calculating_Function
{
    //Driver Class
    class Program
    {
        static void Main(string[] args)
        {
            SeriesCalculation cal = new SeriesCalculation();

            cal.Num = Convert.ToInt64(Console.ReadLine());
            Console.WriteLine(cal.CalculateSeries());
        }
    }

    //Interface
    interface ICalculating_Function
    {
        int CalculateSeries();
    }

    //Main Functional Class
    class SeriesCalculation : ICalculating_Function
    {
        public double Num { get; set; }

        public int CalculateSeries()
        {
            double eNum = 0;
            double oNum = 0;

            if (Num % 2 == 0)
            {
                eNum = Num / 2;
                oNum = Num / 2;
            }
            else
            {
                eNum = Num / 2;
                oNum = (Num / 2) + 1;
            }

            double oddNum = Math.Pow(oNum,2);
            double evNum = eNum * (eNum + 1);

            double res = evNum - oddNum;

            int inRes = (int)Math.Ceiling(res);

            return inRes;
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;

namespace ConsoleApp9
{
    class Program
    {
        static void Main(string[] args)
        {
            var n = int.Parse(Console.ReadLine());
            var result = 0;

            if (n % 2 == 1) { result = (n - 1) / 2; }
            else { result = n / 2; }

            Console.WriteLine(result);

            Console.ReadLine();

        }
    }
}

using System;

namespace CF_Function {
    class Program {
        static void Main(string[] args) {
            string input = Console.ReadLine();
            input = input.Replace("-", "+");
            input = input.Remove(0,1);
            string[] inputs = input.Split('+');
            if(inputs.Length % 2 == 0) {
                Console.WriteLine(inputs.Length / 2);
                return;
            }
            Console.WriteLine(-(inputs.Length+1) /2);
        }
    }
}

using System;
using System.Collections;
using System.Collections.Generic;
class Solution
{
    static void Main(string[] args)
    {
        long n = Convert.ToInt64(Console.ReadLine());
        long evencount = n/2,oddcount=n/2;
        if (n % 2 == 1) oddcount = (n + 1) / 2;
        long oddsum = (oddcount*(-2+(oddcount-1)*-2))/2;
        long evensum = (evencount * (4 + (evencount - 1) * 2))/2;
        Console.Write(oddsum + evensum);
    }
}

using System;
using System.Collections;
using System.Collections.Generic;
class Solution
{
    static void Main(string[] args)
    {
        decimal n = Convert.ToDecimal(Console.ReadLine());
        decimal evencount = n/2,oddcount=n/2;
        if (n % 2 == 1) oddcount = (n + 1) / 2;
        decimal oddsum = (oddcount*(-2+(oddcount-1)*-2))/2;
        decimal evensum = (evencount * (4 + (evencount - 1) * 2))/2;
        Console.Write(oddsum + evensum);
    }
}

using System;
using static System.Console;
using static System.Math;

namespace ConsoleApp8
{
    class Program
    {
        static int Main(string[] args)
        {
            long a=int.Parse(ReadLine());
            if (a % 2 == 0) WriteLine($"{a/2}");
            else WriteLine($"{(a+1)/2*-1-1}");
            return 0;
        }
    }
}

using System;
using static System.Console;
using static System.Math;

namespace ConsoleApp8
{
    class Program
    {
        static int Main(string[] args)
        {
            long a=int.Parse(ReadLine());
            if (a % 2 == 0) WriteLine($"{a - 2}");
            else WriteLine($"{a * -1 + 2}");
            return 0;
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Double n = Double.Parse(Console.ReadLine());
            Console.WriteLine((Math.Floor(n/2)*(Math.Floor(n/2)+1))-(Math.Pow(Math.Ceiling(n/2),2)));
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Int64 n = Int64.Parse(Console.ReadLine()),sum,sumE;
            sum=(n*(n+1))/2;
            sumE=((n%2==0)?(n/2)*((n/2)+1):((n-1)/2)*(((n-1)/2)+1));
            Console.WriteLine(sumE+(-1*(sum-sumE)));
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            UInt64 n = UInt64.Parse(Console.ReadLine()),nE,nO;
            nE = n / 2;
            nO = (n % 2 == 0) ? n/2 : (n/2)+ 1;
           Console.WriteLine(((nE % 2 == 0) ? (nE * (nE + 1)) : Math.Pow(nE, 2)) - Math.Pow(nO, 2));
        }
    }
}

using System;
using System.Linq;
using System.Collections.Generic;
class Program
{
  public static void Main(string[] args)
  {
     long w = Convert.ToInt64(Console.ReadLine());
     Console.WriteLine((w-2)*(w%2==0?1:-1));
  }
}

using System;

namespace Подсчёт_функции
{
    class Program
    {
        static void Main(string[] args)
        {
            Int64 n = Convert.ToInt64(Console.ReadLine());
            Int64 sum = 0;
            if (n % 2 != 0)
            {
                sum = ((n - 1) / 2) - n;
            }
            else
            {
                sum /= 2;
            }
            Console.WriteLine(sum);
        }
    }
}

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using System.Numerics;
using System.Globalization;

namespace Smth
{
    class Program
    {
        public static void Main()
        {
            var n = long.Parse(Console.ReadLine());
            Console.WriteLine((n / 2 + 1) * (n % 2 == 0 ? 1 : -1));
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;

namespace BulkaProga
{
    class Program
    {
        static void Main(string[] args)
        {
            long count = long.Parse(Console.ReadLine());
            Console.WriteLine(count / 2 == 0 ? -(count + 1) / 2 : (count + 1) / 2);
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;

namespace BulkaProga
{
    class Program
    {
        static void Main(string[] args)
        {
            long count = long.Parse(Console.ReadLine());
            Console.WriteLine(-(count + 1) / 2);
        }
    }
}