#include <bits/stdc++.h>
using namespace std;
long long sum(long long n) {
  if (n < 2) return 0;
  long long ans = n * (n + 1) / 2;
  ans--;
  return ans;
}
int main() {
  std::ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long n;
  cin >> n;
  if (n <= 3) {
    cout << 0 << endl;
    return 0;
  }
  long long ans = 0;
  for (long long i = 2; i <= n - 1; i++) {
    long long last = n / i;
    ans += sum(last);
  }
  ans *= 4;
  cout << ans << endl;
}
