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

public class Solution {
    static int i,sum = 1,sum1 = 0;
    static long sumOfGroup(int k) {
       for(int i = 0; i < k + 2; i++){
        sum += 2;
        if(i >= k-1){
            sum1 += sum;
        }   
       
       }
        return sum1;
    }

    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();
    }
}