#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    long cur = 1;
    if (k == 1)
        return 1;
    if (k == 2)
        return 8;
    for (int i = 0; i < k - 2; ++i)
    {
        //std::cout << i << " sum - " << cur << std::endl;
        for (int j = 0; j <= i + 1; ++j)
        {
            cur += 2; 
        }
    }
    long sum = 0;
    for (int j = 0; j < k; ++j)
    {
        cur += 2;
        //std::cout << cur << " ";
        sum += cur;
    }
    //std::cout << std::endl;
    return sum;
}

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