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;
template <class T>
void show(const vector<T> &a) {
  for (T x : a) cout << x << " ";
  cout << '\n';
}
const long long sze = 3e5 + 50, oo = 1e18 + 500, mod = 1000000007;
const long double eps = 5e-10, PI = 2 * acos(0.0);
vector<long long> vertices[sze];
vector<char> visit(sze, false);
vector<long long> arr(sze, 0);
long long n, m, k;
long long d = 0;
long long cnt = 0;
string s;
long long x, y;
bool sv[sze];
signed main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  cin >> n;
  for (long long i = 2; i <= n / 2; i++) {
    for (long long j = 2; j <= n / 2; j++) {
      if (i * j <= n) {
        cnt += j;
      } else {
        break;
      }
    }
  }
  cout << 4 * cnt;
  return 0;
}
