#include <bits/stdc++.h>
using namespace std;
const int len = 1e5 + 9;
const long long mod = 1e9 + 7;
const unsigned long long seed = 131;
int main() {
  long long n;
  cin >> n;
  long long ans = 0;
  for (int i = 2; i <= n; ++i) {
    long long x = n / i;
    ans += (x - 1) * (x + 2) / 2;
  }
  cout << ans * 4 << endl;
}
