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

public class Solution {

    static long sumOfGroup(int k) {
        
        long sum =0;
        
        if (k==1){
            sum =1;
        }else if(k>1){
            int e=1;
            for (int i=1; i<k; i++){
                e=e+2;
               // System.out.println(e);
            }
            
           // System.out.println("final element"+ e);
            for(int i=0;i<k;i++){
                e=e+2;
                sum=sum+e;
              //  System.out.println(e);
            }
            //System.out.println("final sum"+ sum);
        }
        
        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();
    }
}