#include <bits/stdc++.h>
using namespace std;
bool chPrime(int n) {
  int p = sqrt(n) + 1;
  for (int i = 2; i < p; ++i)
    if (!(n % i)) return false;
  return true;
}
int main() {
  int n;
  cin >> n;
  long long count = 0;
  for (int i = 2; i <= n; ++i) {
    long long m = n / i;
    count = (count + (m * (m + 1)) / 2) - 1;
  }
  if (n >= 4)
    cout << 4 * count << endl;
  else
    cout << 0 << endl;
  return 0;
}
