#include <bits/stdc++.h>
using namespace std;
const long long N = 100001;
long long n, maxm = 0;
int32_t main() {
  cin >> n;
  long long ans = 0;
  for (long long i = 2; i <= n; ++i) {
    for (long long j = i << 1; j <= n; j += i) {
      ans += 4 * (j / i);
    }
  }
  cout << ans << endl;
}
