#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n;
  scanf("%lld", &n);
  long long res = 0;
  for (long long d = 2; d < n; ++d)
    for (long long x = 2; d * x <= n; ++x) res += x * 4;
  printf("%lld", res);
  return 0;
}
