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

public class Solution {

    static long sumOfGroup(long k) {
        if (k==1)
            return 1;
        
        else{
        long firstOdd = ((k * (k-1))/2);
        firstOdd = (2 * firstOdd) + 1; 
            
            long sum = 0;
            for(int i = 1 ; i <= k ; i++){
                sum = sum + firstOdd; 
                firstOdd += 2;
            }
            
          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();
    }
}