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

public class Solution {

    static long sumOfGroup(long k) {
           long j,l;
    long sum=0;
    if(k==1)
        return 1;
    else
    {
        j=k*(k-1)+1;
        l=(k+1)*k-1;
        for(long i=j;i<=l;i=i+2)
        {
            sum=sum+i;
        }
        return sum;
    }
    }

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