def solve(n):

    ans=0

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

        c=n//d

        ans+=(c+1)*c//2*d

    return ans



n=int(eval(input()))

print((solve(n)))

# O(sqrt(N))solution



def solve(n):

    ans = 0

    r = n

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

        l = n // (c + 1)

        if r - l == 1: break

        ans += (l + 1 + r) * (r - l) // 2 * c * (c + 1) // 2

        r = l

    for d in range(1, r + 1):

        c = n // d

        ans += (c + 1) * c // 2 * d

    return ans



n=int(eval(input()))

print((solve(n)))

def solve(n):
    ans = 0
    for d in range(1, n + 1):
        c = n // d
        ans += (c + 1) * c // 2 * d
    return ans


n = int(eval(input()))
print((solve(n)))

# O(sqrt(N))solution
def solve(n):
    ans = 0
    r = n
    for c in range(1, n + 1):
        l = n // (c + 1)
        if r - l == 1:
            break
        ans += (l + 1 + r) * (r - l) // 2 * c * (c + 1) // 2
        r = l
    for d in range(1, r + 1):
        c = n // d
        ans += (c + 1) * c // 2 * d
    return ans


n = int(eval(input()))
print((solve(n)))

+# O(sqrt(N))solution -    for d in range(1, n + 1): +    r = n +    for c in range(1, n + 1): +        l = n // (c + 1) +        if r - l == 1: +            break +        ans += (l + 1 + r) * (r - l) // 2 * c * (c + 1) // 2 +        r = l +    for d in range(1, r + 1):