#include <fstream>
using namespace std;

int main(void)
{
    fstream fin("sarpe.in",ios::in);
    fstream fout("sarpe.out",ios::out);

    long long N;
    fin >> N;

    if (N == 1)
    {
        fout << 2;
    }
    else
    {
        fout << ((4 * N) + (2 * (N - 1) * (N - 2)));
    }

    fin.close();
    fout.close();
    return 0;
}