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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.*;

public class Main {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int n = input.nextInt()-1;
        int a[]=new int[18258];
        a[0]=1;
        a[1]=13;
        for (int i=2; i<=n; i++) {
            
            a[i]=12*i+a[i-1];
        }
        System.out.println(a[n]);
    }
}
