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

public class Solution {

    static long sumOfGroup(int k) {
        int[] ar=new int[k];
        int j=k+k,p=1,i,sum=0;
        for(i=0;i<k;i++)
        {
            p=p+2;
        }
        for(i=0;i<k;i++)
        {
            ar[i]=p;
            p=p+2;
        }
        
        for(i=0;i<k;i++)
        {
            sum=sum+ar[i];
        }
        return(sum);
        // Return the sum of the elements of the k'th group.
    }

    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();
    }
}