using System;

public class Program

{

    public static void Main()

    {

        //Diego Suarez Galindo

        int position;

        int num = 3;

        Console.WriteLine("3, 9, 21, 45…");

        Console.WriteLine("Position");

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

        for (int i = 2; i < position; i++)

        {

            num = 2 *num + 3;

        }

​

        Console.WriteLine(num);

    }

}

​