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

public class Solution {

    static long sumOfGroup(int k) {
        int m =0 ;
        ArrayList<Integer> arr = new ArrayList<>();

        for(int j =0 ; j< k*(k+1) ; j++){
            if(j % 2 != 0 ){
                arr.add(j);
            }
        }

        for( int i = arr.size()-1; i > arr.size()-k-1; i-- ){
            m+= arr.get(i);

        }
        return m;
    }

    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();
    }
}