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

public class Solution {

    static long sumOfGroup(int k) {
        // Return the sum of the elements of the k'th group.
        long group = k;
        long sum = 0;
        long i = 0;
            
            long high = (long)Math.pow(group,2)+(group-1);
            long low = (long)Math.pow(group,2)-(group-1);
            for (i = low;i <= high;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();
    }
    
    
}