#include <bits/stdc++.h>
using namespace std;
long long n, ans;
int main() {
  scanf("%I64d", &n);
  for (long long i = 2; i <= n; i++) {
    for (long long j = i + i; j <= n; j += i) {
      ans += (j / i);
    }
  }
  printf("%I64d\n", ans * 4ll);
  return 0;
}
