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[]arr=new long[k+(k-1)*k/2];
		 long sum=0;
		 long z=0;
		 for(long j=0;j<arr.length;j++)
		 {
			 arr[(int)j]=2*j+1;
		 }
		 if(k%2!=0)
		 {
			  z=k*((k-1)/2);
			  for(long p=z;p<=k+z-1;p++)
				 {
					 sum+=arr[(int)p];
				 }
		 }
		 else if(k%2==0)
		 {
			 z = k*(k/2)-(k/2);
			 for(long p=z;p<=k+z-1;p++)
			 {
				 sum+=arr[(int)p];
			 }
		 }
		 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();
    }
}