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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.awt.Point;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;


public class CF_C {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        int[] vals=new int[18258];
        vals[1]=1;
        for(int i=2;i<vals.length;i++)
            vals[i]=vals[i-1]+6*((i-2)*2+1)+6;
        System.out.println(vals[sc.nextInt()]);
    }
}
