using System;
public class Program
{
public static void Main()
//Eduardo castillo
int pos;
int num = 4;
Console.WriteLine("4, 13, 31, 67");
Console.WriteLine("From the previous series, what position would you like to know");
pos = int.Parse (Console.ReadLine());
for (int i = 4; i <=pos; i++)
num = 4*num + 1;
}
Console.WriteLine(num);
