N = int(eval(input()))



def solve():

    ans = 0

    for k in range(1,N+1):

        d = N//k

        ans += k*d*(d+1)//2

    return ans



if __name__ == "__main__":

    print((solve()))

import numpy as np

n = int(eval(input()))

k = np.arange(1,n+1)

d = n // k

print(((k*d*(d+1)//2).sum()))
N = int(eval(input()))


def solve():
    ans = 0
    for k in range(1, N + 1):
        d = N // k
        ans += k * d * (d + 1) // 2
    return ans


if __name__ == "__main__":
    print((solve()))

import numpy as np

n = int(eval(input()))
k = np.arange(1, n + 1)
d = n // k
print(((k * d * (d + 1) // 2).sum()))

-N = int(eval(input())) +import numpy as np - -def solve(): -    ans = 0 -    for k in range(1, N + 1): -        d = N // k -        ans += k * d * (d + 1) // 2 -    return ans - - -if __name__ == "__main__": -    print((solve())) +n = int(eval(input())) +k = np.arange(1, n + 1) +d = n // k +print(((k * d * (d + 1) // 2).sum()))