### BUGGY CODE ###

import sys

def input(): return sys.stdin.readline().strip()
def list2d(a, b, c): return [[c] * b for i in range(a)]
def list3d(a, b, c, d): return [[[d] * c for j in range(b)] for i in range(a)]
def list4d(a, b, c, d, e): return [[[[e] * d for j in range(c)] for j in range(b)] for i in range(a)]
def ceil(x, y=1): return int(-(-x // y))
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(N=None): return list(MAP()) if N is None else [INT() for i in range(N)]
def Yes(): print('Yes')
def No(): print('No')
def YES(): print('YES')
def NO(): print('NO')
sys.setrecursionlimit(10 ** 9)
INF = 10 ** 19
MOD = 10 ** 9 + 7
EPS = 10 ** -10

def factorize(N):
    def gcd(a, b):
        while b: a, b = b, a % b
        return a
    def isPrimeMR(n):
        d = n - 1
        d = d // (d & -d)
        L = [2]
        for a in L:
            t = d
            y = pow(a, t, n)
            if y == 1: continue
            while y != n - 1:
                y = (y * y) % n
                if y == 1 or t == n - 1: return 0
                t <<= 1
        return 1
    def findFactorRho(n):
        m = 1 << n.bit_length() // 8
        for c in range(1, 99):
            f = lambda x: (x * x + c) % n
            y, r, q, g = 2, 1, 1, 1
            while g == 1:
                x = y
                for i in range(r):
                    y = f(y)
                k = 0
                while k < r and g == 1:
                    ys = y
                    for i in range(min(m, r - k)):
                        y = f(y)
                        q = q * abs(x - y) % n
                    g = gcd(q, n)
                    k += m
                r <<= 1
            if g == n:
                g = 1
                while g == 1:
                    ys = f(ys)
                    g = gcd(abs(x - ys), n)
            if g < n:
                if isPrimeMR(g): return g
                elif isPrimeMR(n // g): return n // g
                return findFactorRho(g)
    def primeFactor(n):
        i = 2
        ret = {}
        rhoFlg = 0
        while i*i <= n:
            k = 0
            while n % i == 0:
                n //= i
                k += 1
            if k: ret[i] = k
            i += 1 + i % 2
            if i == 101 and n >= 2 ** 20:
                while n > 1:
                    if isPrimeMR(n):
                        ret[n], n = 1, 1
                    else:
                        rhoFlg = 1
                        j = findFactorRho(n)
                        k = 0
                        while n % j == 0:
                            n //= j
                            k += 1
                        ret[j] = k
        if n > 1: ret[n] = 1
        if rhoFlg: ret = {x: ret[x] for x in sorted(ret)}
        return ret
    return primeFactor(N)

N = INT()

ans = 0
for i in range(1, N+1):
    res = factorize(i)
    cnt = 1
    for v in res.values():
        cnt *= v + 1
    ans += cnt * i
print(ans)


### FIXED CODE ###

import sys

def input(): return sys.stdin.readline().strip()
def list2d(a, b, c): return [[c] * b for i in range(a)]
def list3d(a, b, c, d): return [[[d] * c for j in range(b)] for i in range(a)]
def list4d(a, b, c, d, e): return [[[[e] * d for j in range(c)] for j in range(b)] for i in range(a)]
def ceil(x, y=1): return int(-(-x // y))
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(N=None): return list(MAP()) if N is None else [INT() for i in range(N)]
def Yes(): print('Yes')
def No(): print('No')
def YES(): print('YES')
def NO(): print('NO')
sys.setrecursionlimit(10 ** 9)
INF = 10 ** 19
MOD = 10 ** 9 + 7
EPS = 10 ** -10

def eratosthenes_sieve(n):
    table = [0] * (n+1)
    for i in range(1, n+1):
        for j in range(i, n+1, i):
            table[j] += 1
    return table

N = INT()

res = eratosthenes_sieve(N)
ans = 0
for i in range(1, N+1):
    ans += res[i] * i
print(ans)