#include <bits/stdc++.h>
#define ll long long

using namespace std;

ll sumOfGroup(ll k) {
    // Return the sum of the elements of the k'th group.
    ll index = k*(k-1) + 1;
    ll sum = 0;
    for (ll i =0;i<k;i++)
        sum += (index+i*2);
    return sum;
}

int main() {
    ll k;
    cin >> k;
    ll answer = sumOfGroup(k);
    cout << answer << endl;
    return 0;
}