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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 {

    void run(){
        Scanner scan=new Scanner(System.in);
        int n=scan.nextInt();
        long edge=12;
        long sum=1;
        for(int i=2;i<=n;i++){
            sum+=edge;
            edge+=12;
            sum%=2000000000;
            edge%=2000000000;
        }
        System.out.println(sum);
    }
    public static void main(String[] args) {
        new Main().run();

    }

}
