#include <bits/stdc++.h>
using namespace std;
const int N = 100000 + 10;
const int M = 1000000007;
const double eps = 1e-9;
const double PI = acos(-1);
const int oo = 1000000000;
int n;
int main() {
  cin >> n;
  long long ans = 0;
  for (int i = 2; i <= n / 2; ++i)
    for (int j = i + i; j <= n; j += i) ans += j / i * 4;
  cout << ans << endl;
  return 0;
}
