!! Really Strange !!

import java.math.BigInteger;
import java.util.Scanner;

public class Main {

    public static void main(String[]args){

        BigInteger n,a,b;

        Scanner sc = new Scanner(System.in);

        while(sc.hasNext()){

            n = sc.nextBigInteger();

            if(n.equals(BigInteger.ZERO)){
                System.out.println("1");
                continue;
            }
            a = n.subtract(BigInteger.ONE);

            b = BigInteger.ONE;

            b = b.add(b);

            System.out.println((n.multiply(a)).add(b));
        }
    }
}