#include <bits/stdc++.h>
using namespace std;
const int N = 100005;
long long i, j, n;
int ar[N];
int main() {
  for (int i = 2; i < N; i++) {
    for (int j = i + i; j < N; j += i) {
      ar[j] += j / i;
    }
  }
  cin >> n;
  long long sum = 0;
  for (int i = 2; i <= n; i++) sum += ar[i];
  cout << 4 * sum << endl;
}
