You are given a positive integer n greater or equal to 2. For every pair of integers a and b (2 ≤ |a|, |b| ≤ n), you can transform a into b if and only if there exists an integer x such that 1 < |x| and (a ⋅ x = b or b ⋅ x = a), where |x| denotes the absolute value of x.

After such a transformation, your score increases by |x| points and you are not allowed to transform a into b nor b into a anymore.

Initially, you have a score of 0. You can start at any integer and transform it as many times as you like. What is the maximum score you can achieve?

Input

A single line contains a single integer n (2 ≤ n ≤ 100 000) — the given integer described above.

Output

Print an only integer — the maximum score that can be achieved with the transformations. If it is not possible to perform even a single transformation for all possible starting integers, print 0.

Examples

Input

4


Output

8

Input

6


Output

28

Input

2


Output

0

Note

In the first example, the transformations are 2 → 4 → (-2) → (-4) → 2.

In the third example, it is impossible to perform even a single transformation.
#include <bits/stdc++.h>
using namespace std;
inline long long gcd(long long a, long long b) { return b ? gcd(b, a % b) : a; }
inline long long lcm(long long a, long long b) { return a / gcd(a, b) * b; }
int month[15] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
int dir[8][2] = {{-1, 0},  {1, 0}, {0, -1}, {0, 1},
                 {-1, -1}, {1, 1}, {1, -1}, {-1, 1}};
const int MAXN = 1e5 + 5;
const int INF = 1 << 30;
const long long mod = 1e9 + 7;
const double eps = 1e-8;
const long long inff = 0x3f3f3f3f3f3f3f3f;
long long n, p, m, k, cnt, a[25], ans = 0;
bool vis[MAXN];
int main() {
  cin >> n;
  m = n / 2 + 3;
  for (int i = 2; i <= m; i++) {
    k = n / i - 1;
    if (k > 0) ans += i * 4 * k;
  }
  cout << ans << endl;
}
