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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.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class B {


    public static void main(String[] args) throws IOException {
                BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
          StringTokenizer st;


    a1: do {
                    st= new StringTokenizer(br.readLine());
                    long x=Long.parseLong(st.nextToken());
                    long res = (6*x*x)-(6*x)+1;
                    System.out.println(res);

                        }while (br.ready());

    }// End of main method

}// End of class