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;
		
		long startSum = 0;
		for(long i = 1; i < k; i++){
			startSum += i;
		}
		//System.out.println(startSum);
		startSum *= 2;
		k--;
		long end = startSum + (k * 2);
		end++;
		startSum++;
		//System.out.println(startSum+" "+end);
		
        for(long i = startSum; i <= end; i += 2){
            
        	sum += i;
        	
        }
        
        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();
    }
}