#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e5 + 10;
int main() {
  int n;
  cin >> n;
  long long ans = 0;
  for (int i = 2; i < n; i++) {
    for (int j = i * 2; j <= n; j += i) {
      ans += j / i * 4;
    }
  }
  printf("%I64d\n", ans);
  return 0;
}
