import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    static long sumOfGroup(int k) {
        // Return the sum of the elements of the k'th group.
        long m=1;
        long value=0,sum=0;
        if(k==1)
            return 1;
        else if(k==2)
            return 9;
        for(int i=2;i<k;i++)
        {
            m+=i;
        }
        
          value=m*2+1;
           sum=value;
          for(int i=1;i<k;i++)
          {
              value+=2;
              sum+=value;
          }
        
        return sum;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int k = in.nextInt();
        long answer = sumOfGroup(k);
        System.out.println(answer);
        in.close();
    }
}