#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

long long sumOfGroup(int k) {
    ll k1 = ((ll)k*((ll)k-1))/2;
    ll st = 1 + (k1)*2;
    ll sum = 0;
    ll lt = st + (k-1)*2;
    return (lt + st)*k/2;
}

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