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Input

The input contains a single integer a (1 ≤ a ≤ 18257).

Output

Print a single integer output (1 ≤ output ≤ 2·109).

Examples

Input

2


Output

13
import java.util.Scanner;


public class Main {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        do
        {
        long n = input.nextLong();
        long resultado = (((3*n-1)*(3*n-2)+(n)*(n-1)*3)/2);
            System.out.println(resultado);
        }while(input.hasNext());
    }
}
