#include <bits/stdc++.h>
using namespace std;
long long n, ans;
int main() {
  scanf("%lld", &n);
  for (int i = 2; i <= n; i++)
    for (int j = (i << 1); j <= n; j += i) ans += j / i;
  printf("%lld", (ans << 2));
  return 0;
}
