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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 sc = new Scanner(System.in);
        int a = sc.nextInt();
        int temp1 = p6(a);
        int temp2 = p3(a*3-2);

        System.out.println(temp2 * 2 - temp1);
    }
    static int p6(int n) {
        return p3(n) * 6 - n * 6 + 1;
    }
    static int p3(int n) {
        return n * (n + 1) / 2;
    }
}