#include <bits/stdc++.h>
using namespace std;

#define ll long long

int main() {
    ll k;
    cin >> k;
    
    ll a = (k * (k-1)) / 2;
    ll b = (k * (k+1)) / 2;
    
    ll ans = (b*(b-1) - a*(a-1)) + (b - a);
    cout << ans << endl;
    
    return 0;
}