#include <bits/stdc++.h>
using namespace std;
int main(int argc, char** argv) {
  long long n, i, j, s = 0;
  cin >> n;
  for (i = 2; i <= n; i++)
    for (j = i * 2; j <= n; j = j + i) s = s + j / i * 4;
  cout << s;
  return 0;
}
