#include <bits/stdc++.h>
using namespace std;
void solve() {
  int n;
  cin >> n;
  long long ans = 0;
  for (auto i = 4; i <= n; ++i) {
    for (auto j = 2; j * j <= i; ++j) {
      if (i % j == 0) {
        ans += i / j * 4;
        if (j * j != i) ans += j * 4;
      }
    }
  }
  cout << ans << endl;
}
int main() {
  cin.sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  solve();
}
