#include <bits/stdc++.h>
using namespace std;
const long long maxn = 1e5 + 5;
const long long INF = 1e18 + 10;
const long long mod = 1e9 + 7;
void solve() {
  long long n;
  cin >> n;
  long long ans = 0;
  for (int i = 2; i <= n; i++) {
    long long x = n / i;
    ans += (2 + x) * (x - 1) * 2;
  }
  cout << ans << endl;
}
int main() { solve(); }
