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


int main() {
    ll k;
    cin >> k;
    ll d = k *(k-1) + 1;
    ll sum = 0;
    while(k--){
        sum += d;
        d+=2;
    }
    cout << sum << endl;
    return 0;
}