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

public class Solution {

   // public static k getkgroup
    
    static long sumOfGroup(int k) {
        int tempk = 0;
        long currentOdd = -1;
        while (tempk != k ){ 
           tempk++;   
           currentOdd+= 2*(tempk);  
        }
        long res = 0;
        for(int i=0; i<k; i++){
            res+=currentOdd;
            currentOdd-=2;
        }
        return res;
    }

    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();
    }
}