#include <bits/stdc++.h>
using namespace std;
const int base = 1000 * 1000 * 1000;
const int mod = 1000 * 1000 * 1000 + 7;
bool isPrime(int x) {
  for (int i = 2; i * i <= x; i++) {
    if (x % i == 0) return false;
  }
  return true;
}
int main() {
  int n;
  cin >> n;
  long long ans = 0;
  for (int i = 2; i <= n; i++) {
    for (int j = 2 * i; j <= n; j += i) {
      ans += 4 * (j / i);
    }
  }
  cout << ans;
  return 0;
}
