#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long int n, i, j, sm = 0;
  cin >> n;
  for (i = 2; i <= n; i++)
    for (j = 2 * i; j <= n; j += i) sm += 4 * (j / i);
  cout << sm;
  return 0;
}
