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