#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n = 0, ans = 0;
  cin >> n;
  if (abs(n) < 4)
    cout << 0;
  else {
    for (int i = 2; i < n; i++) {
      for (int j = i * 2; j <= n; j += i) {
        ans += ((j / i) * 4);
      }
    }
    cout << ans;
  }
  return 0;
}
