def main():

    num = int(eval(input()))

    gg = ((

        (quotient := num // divisor) + 1) * quotient * divisor // 2

        for divisor in range(1, num + 1))

    print((sum(gg)))





if __name__ == '__main__':

    main()

def main():

    num = int(eval(input()))

    ans = 0



    for divisor in range(1, num + 1):

        quotient = num // divisor

        ans += (quotient + 1) * quotient * divisor // 2



    print(ans)





if __name__ == '__main__':

    main()

def main():
    num = int(eval(input()))
    gg = (
        ((quotient := num // divisor) + 1) * quotient * divisor // 2
        for divisor in range(1, num + 1)
    )
    print((sum(gg)))


if __name__ == "__main__":
    main()

def main():
    num = int(eval(input()))
    ans = 0
    for divisor in range(1, num + 1):
        quotient = num // divisor
        ans += (quotient + 1) * quotient * divisor // 2
    print(ans)


if __name__ == "__main__":
    main()

-    gg = ( -        ((quotient := num // divisor) + 1) * quotient * divisor // 2 -        for divisor in range(1, num + 1) -    ) -    print((sum(gg))) +    ans = 0 +    for divisor in range(1, num + 1): +        quotient = num // divisor +        ans += (quotient + 1) * quotient * divisor // 2 +    print(ans)