#include <bits/stdc++.h>
long long ans = 0, n;
int main(int argc, char *argv[]) {
  scanf("%lld", &n);
  for (int i = 2; i <= n; i++)
    for (int j = 2 * i; j <= n; j += i) ans += j / i;
  printf("%lld\n", ans * 4ll);
  return 0;
}
