#include <bits/stdc++.h>
using namespace std;
int a[1000001];
int cnt2[1000001];
void solve() {
  int n;
  cin >> n;
  int64_t ans = 0;
  for (int i = 2; i <= n; ++i) {
    int x = i;
    for (int j = 2; j * j <= x; ++j) {
      if (x % j == 0) {
        ans += 4 * j;
        if (j != x / j) ans += 4 * x / j;
      }
    }
  }
  cout << ans;
}
int main() {
  solve();
  return 0;
}
