import java.util.*;

public class Hackerrank
{
    static long sumOfGroup(int x)
    {
        long k=(long)x;
        long t=1+((k-1)*k);
        long s=k*(2*t+(k-1)*2)/2;
        return s;
    }

    public static void main(String[] args)
    {
        Scanner in = new Scanner(System.in);
        int k = in.nextInt();
        long answer = sumOfGroup(k);
        System.out.println(answer);
        in.close();
    }
}