#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int n, sum = 0;
  cin >> n;
  for (long long int i = 2; (i * 2) <= n; i++) {
    long long int somantor = n / i;
    long long int sumofsomantor = (somantor * (somantor + 1) / 2) - 1;
    sum += sumofsomantor * 4;
  }
  printf("%lld", sum);
}
