def main(N):

    x = 0

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

        b=N//a

        x += a*b*(b+1)//2

    return x

 

N = int(eval(input()))

print((main(N)))
import numba

@numba.njit

def main(N):

    x = 0

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

        b=N//a

        x += a*b*(b+1)//2

    return x

N = int(eval(input()))

print((main(N)))
def main(N):
    x = 0
    for a in range(1, N + 1):
        b = N // a
        x += a * b * (b + 1) // 2
    return x


N = int(eval(input()))
print((main(N)))

import numba


@numba.njit
def main(N):
    x = 0
    for a in range(1, N + 1):
        b = N // a
        x += a * b * (b + 1) // 2
    return x


N = int(eval(input()))
print((main(N)))

+import numba + + +@numba.njit