n=int(eval(input()))

ans=0

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

    x=n//i

    ans+=i*(x+1)*x//2

print(ans)
from numba import jit

@jit(cache = True)

def main():

    n=int(eval(input()))

    ans=0

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

        x=n//i

        ans+=i*(x+1)*x//2

    print(ans)



if __name__ == '__main__':

    main()
n = int(eval(input()))
ans = 0
for i in range(1, n + 1):
    x = n // i
    ans += i * (x + 1) * x // 2
print(ans)

from numba import jit


@jit(cache=True)
def main():
    n = int(eval(input()))
    ans = 0
    for i in range(1, n + 1):
        x = n // i
        ans += i * (x + 1) * x // 2
    print(ans)


if __name__ == "__main__":
    main()

-n = int(eval(input())) -ans = 0 -for i in range(1, n + 1): -    x = n // i -    ans += i * (x + 1) * x // 2 -print(ans) +from numba import jit + + +@jit(cache=True) +def main(): +    n = int(eval(input())) +    ans = 0 +    for i in range(1, n + 1): +        x = n // i +        ans += i * (x + 1) * x // 2 +    print(ans) + + +if __name__ == "__main__": +    main()