import sys



from numba import njit



input = sys.stdin.readline





@njit

def make_n_divisor_table(n):

    table = [0] * (n + 1)

    for i in range(1, n + 1):

        for j in range(i, n + 1, i):

            table[j] += 1

    return table





def main():

    N = int(eval(input()))



    table = make_n_divisor_table(N)



    ans = 0

    for i, v in enumerate(table):

        ans += i * v



    print(ans)





if __name__ == "__main__":

    main()

import sys



import numba as nb



input = sys.stdin.readline





@nb.njit

def solve(n):

    table = [0] * (n + 1)

    for i in range(1, n + 1):

        for j in range(i, n + 1, i):

            table[j] += 1

    ans = 0

    for i, v in enumerate(table):

        ans += i * v

    return ans





def main():

    N = int(eval(input()))



    ans = solve(N)



    print(ans)





if __name__ == "__main__":

    main()

import sys
from numba import njit

input = sys.stdin.readline


@njit
def make_n_divisor_table(n):
    table = [0] * (n + 1)
    for i in range(1, n + 1):
        for j in range(i, n + 1, i):
            table[j] += 1
    return table


def main():
    N = int(eval(input()))
    table = make_n_divisor_table(N)
    ans = 0
    for i, v in enumerate(table):
        ans += i * v
    print(ans)


if __name__ == "__main__":
    main()

import sys
import numba as nb

input = sys.stdin.readline


@nb.njit
def solve(n):
    table = [0] * (n + 1)
    for i in range(1, n + 1):
        for j in range(i, n + 1, i):
            table[j] += 1
    ans = 0
    for i, v in enumerate(table):
        ans += i * v
    return ans


def main():
    N = int(eval(input()))
    ans = solve(N)
    print(ans)


if __name__ == "__main__":
    main()

-from numba import njit +import numba as nb -@njit -def make_n_divisor_table(n): +@nb.njit +def solve(n): -    return table +    ans = 0 +    for i, v in enumerate(table): +        ans += i * v +    return ans -    table = make_n_divisor_table(N) -    ans = 0 -    for i, v in enumerate(table): -        ans += i * v +    ans = solve(N)