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

int64_t f(int64_t k)
{
    return 2 * k * (k + 1) + 1;
}

int main()
{
    int64_t k;
    cin >> k;
    cout << f(k) + f(k - 1) << endl;
    return 0;
}