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;
long long in() {
  long long a;
  scanf("%lld", &a);
  return a;
}
double din() {
  double a;
  scanf("%lf", &a);
  return a;
}
long long bigmod(long long b, long long p, long long md) {
  if (p == 0) return 1;
  if (p % 2 == 1) {
    return ((b % md) * bigmod(b, p - 1, md)) % md;
  } else {
    long long y = bigmod(b, p / 2, md);
    return (y * y) % md;
  }
}
long long gcd(long long a, long long b) {
  if (b == 0)
    return a;
  else
    return gcd(b, a % b);
}
long long getRandom(long long a, long long b) {
  long long ret = (long long)rand() * (long long)rand();
  ret %= (b - a + 1);
  ret += a;
  return ret;
}
int main() {
  long long n = in(), ans = 0;
  for (long long i = 2; i <= n; i++) {
    long long x = n / i;
    ans += max(0LL, 2 * ((x * (x + 1)) - 2));
  }
  printf("%lld\n", (long long)ans);
}
