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