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

public class Solution {

    static long sumOfGroup(long k) {
        long result = 0;
        
        long number = k + (k - 1) * (k - 1); 
        
        for(long i =0 ; i < k; i++){
            result += number;
            number += 2;
        }
        
        return result;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        long k = in.nextLong();
        long answer = sumOfGroup(k);
        System.out.println(answer);
        in.close();
    }
}