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

n=int(eval(input()))



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

n_max=n//n_min*n_min

kousu=n//n_min



print(((kousu*(n_min+n_max)//2).sum()))
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

n = int(eval(input()))
n_min = np.arange(1, n + 1, dtype=np.int64)
n_max = n // n_min * n_min
kousu = n // n_min
print(((kousu * (n_min + n_max) // 2).sum()))

-from sys import stdin - -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() +n = int(eval(input())) +n_min = np.arange(1, n + 1, dtype=np.int64) +n_max = n // n_min * n_min +kousu = n // n_min +print(((kousu * (n_min + n_max) // 2).sum()))