using System;

public class Program

{

    public static void Main()

    {

        //Luisa Weissbach

        int num, num2; 

        num= 4; 

        Console.WriteLine(" 4, 13, 31, 67... What position would you like to know:");

        num2 = int.Parse(Console.ReadLine());

        for (int c = 2; c<=num2; c++)

        {

            num = num *2 + 5; 

        }

        Console.WriteLine(num); 

    }

}