from math import sqrt


def f(n): 
  
    hh = [1] * (n + 1); 
      
    p = 2; 
    while((p * p) < n): 
        if (hh[p] == 1): 
            for i in range((p * 2), n, p): 
                hh[i] = 0; 
        p += 1; 
  
    total = 1; 
    for p in range(2, n + 1): 
        if (hh[p] == 1): 
            count = 0; 
            if (n % p == 0): 
                while (n % p == 0): 
                    n = int(n / p); 
                    count += 1; 
                total *= (count + 1); 
                  
    return total; 


def main():
    n=int(input())
    a=0
    for k in range(1, n+1):
        a+=k*f(k)
    print(a)


if __name__=='__main__':
    main()

from math import sqrt


def f(n): 
  
    hh = [1] * (n + 1); 
      
    p = 2; 
    while((p * p) < n): 
        if (hh[p] == 1): 
            for i in range((p * 2), n, p): 
                hh[i] = 0; 
        p += 1; 
  
    total = 1; 
    for p in range(2, n + 1): 
        if (hh[p] == 1): 
            count = 0; 
            if (n % p == 0): 
                while (n % p == 0): 
                    n = int(n / p); 
                    count += 1; 
                total *= (count + 1); 
                  
    return total; 


def main():
    n=int(input())
    a=0
    for k in range(1, n+1):
        a+=k*f(k)
    print(a)


if __name__=='__main__':
    main()
