#include<fstream>

using namespace std;

short n;
int main()
{
    ifstream fin("sarpe.in");
    ofstream fout("sarpe.out");
fin>>n;
if(n == 1)
fout<<2;
else
fout<<4*n + 2*(n-1)*(n-2);

fin.close();
fout.close();

return 0;

}