#include <bits/stdc++.h>
using namespace std;
template <typename T, typename U>
inline void smin(T &a, const U &b) {
  if (a > b) a = b;
}
template <typename T, typename U>
inline void smax(T &a, const U &b) {
  if (a < b) a = b;
}
int main() {
  int n;
  cin >> n;
  long long ans = 0;
  for (int i = 2; i <= n; i++)
    for (int j = i; j <= n; j += i)
      if (i != j) {
        ans += 4 * j / i;
      }
  cout << ans << endl;
}
