#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  long long sum = 0;
  scanf("%d", &n);
  for (int i = 2; i <= n; ++i) {
    if (2 * i > n)
      break;
    else {
      long long q = n / i;
      sum = sum + q * (q + 1) / 2 - 1;
    }
  }
  cout << 4 * sum << '\n';
  return 0;
}
