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 sum =0;
        long num =1;
        int l =1;
        for(int i =1 ;i<k;i++)
        {
            if(i>1)
            {
            for(int j = 1;j<=l; j++)
            {
                num +=2;
            }
            }
            l++;
        }
       // sum = num;
        num = num+2;
        for(int i =0; i<k; i++)
        {
            sum += num;
            num+=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();
    }
}