#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    // Return the sum of the elements of the k'th group.
    long i = 1;
    for (int j = 1; j < k; j++)
    {
        // find first element of group k
        for (int m = 1; m <= j; m++)
            i += 2;
    }
    
    long sum = i;
    for (int j = 1; j < k; j++)
    {
        i += 2;
        sum += i;
    }
    
    return sum;
}

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