import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		long k = sc.nextInt();
		sc.close();

		long v1 = (2 * k + 1) * k;
		long v2 = (2 * k - 1) * (k - 1);
		System.out.println(v1 + v2 + k + k + 1);
	}
}