import sys

read = sys.stdin.read

readline = sys.stdin.readline

readlines = sys.stdin.readlines

#import numpy as np

def main():

    n = int(eval(input()))

    if n == 1:

        print((1))

        sys.exit()

    r = 0

    for i1 in range(1, n + 1):

        num_of_div = n // i1

        r += num_of_div * (num_of_div + 1) // 2 * i1

    print(r)



if __name__ == '__main__':

    main()

import sys

read = sys.stdin.read

readline = sys.stdin.readline

readlines = sys.stdin.readlines

import numpy as np

def main():

    n = int(eval(input()))

    if n == 1:

        print((1))

        sys.exit()

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

    divs2 = n // divs

    divs3 = divs2 * (divs2 + 1) // 2

    divs3 = divs3 * divs

    r = divs3.sum()

    print(r)



if __name__ == '__main__':

    main()

import sys

read = sys.stdin.read
readline = sys.stdin.readline
readlines = sys.stdin.readlines
# import numpy as np
def main():
    n = int(eval(input()))
    if n == 1:
        print((1))
        sys.exit()
    r = 0
    for i1 in range(1, n + 1):
        num_of_div = n // i1
        r += num_of_div * (num_of_div + 1) // 2 * i1
    print(r)


if __name__ == "__main__":
    main()

import sys

read = sys.stdin.read
readline = sys.stdin.readline
readlines = sys.stdin.readlines
import numpy as np


def main():
    n = int(eval(input()))
    if n == 1:
        print((1))
        sys.exit()
    divs = np.arange(1, n + 1)
    divs2 = n // divs
    divs3 = divs2 * (divs2 + 1) // 2
    divs3 = divs3 * divs
    r = divs3.sum()
    print(r)


if __name__ == "__main__":
    main()

-# import numpy as np +import numpy as np + + -    r = 0 -    for i1 in range(1, n + 1): -        num_of_div = n // i1 -        r += num_of_div * (num_of_div + 1) // 2 * i1 +    divs = np.arange(1, n + 1) +    divs2 = n // divs +    divs3 = divs2 * (divs2 + 1) // 2 +    divs3 = divs3 * divs +    r = divs3.sum()