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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)  throws Exception{
        new Main().run();
    }
    
    private void run() throws Exception{
        Scanner input = new Scanner(System.in);
        int num = input.nextInt();
        System.out.println(6*(num-1)*(num)+1);
        
    }
}