using System;

using System.Diagnostics;

public class Program

{

    public static void Main() 

    {

        NumDecodings("a");

    }

    public static void NumDecodings(string s)

    {

        str = "1234";

        Console.WriteLine(Decode(0, 0));

    }

    static string str;

    public static int Decode(int pos, int read)

    {

        Console.WriteLine("{0} ..:.. {1}", pos, read);

        if(pos >= str.Length) return 0;

        if(read == 2 && (str[pos] - '0') > 2)

        {

            Console.WriteLine("end");

            return Decode(pos + 1, 1);

        }

        if(read == ((str.Length) - pos)) {

            return 1;

        }

        return Decode(pos + read, 2) + Decode(pos + read, 1);

    }

}