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

long sumOfGroup(ll k) {
    ll num=k*(k-1)+1;
    ll sum=k*(2*num+(k-1)*2)/2;
    return sum;
    // Return the sum of the elements of the k'th group.
}

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