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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 cin = new Scanner(System.in);
        while (cin.hasNext()){
            long a = cin.nextLong();
            long r = f(a);
            System.out.println(r);
            
        }
    }   
    public static long f(long a){       
        return 6 * a * a - 6 * a  + 1;
    }
}
