from sys import stdin

def main():

    #入力

    readline=stdin.readline

    n=int(readline())



    ans=0

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

        n_min=i

        n_max=n//i*i

        ans+=(n//i)*(n_min+n_max)//2



    print(ans)



if __name__=="__main__":

    main()
from sys import stdin

import numpy as np

def main():

    #入力

    readline=stdin.readline

    n=int(readline())



    ans=0

    n_min=np.arange(1,n+1,dtype=np.int64)

    n_max=n//n_min*n_min

    kousu=n//n_min

    ans=(kousu*(n_min+n_max)//2).sum()



    print(ans)



if __name__=="__main__":

    main()
from sys import stdin


def main():
    # 入力
    readline = stdin.readline
    n = int(readline())
    ans = 0
    for i in range(1, n + 1):
        n_min = i
        n_max = n // i * i
        ans += (n // i) * (n_min + n_max) // 2
    print(ans)


if __name__ == "__main__":
    main()

from sys import stdin
import numpy as np


def main():
    # 入力
    readline = stdin.readline
    n = int(readline())
    ans = 0
    n_min = np.arange(1, n + 1, dtype=np.int64)
    n_max = n // n_min * n_min
    kousu = n // n_min
    ans = (kousu * (n_min + n_max) // 2).sum()
    print(ans)


if __name__ == "__main__":
    main()

+import numpy as np -    for i in range(1, n + 1): -        n_min = i -        n_max = n // i * i -        ans += (n // i) * (n_min + n_max) // 2 +    n_min = np.arange(1, n + 1, dtype=np.int64) +    n_max = n // n_min * n_min +    kousu = n // n_min +    ans = (kousu * (n_min + n_max) // 2).sum()