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