using System;

using System.IO;

using System.Collections.Generic;

​

public class Program

{

    public static IEnumerable<string> GetStuff(string input)

    {

        Console.WriteLine(input.Length);

        if (input.Length == 46)

            yield return input.Substring(4, 40);

        else

            for (var i = 0; i < input.Length; i += 44)

                yield return input.Substring(i + 2, 40);

    }

​

    public static void Main()

    {

        var input = "xxxx1234567890123456789012345678901234567890xx";

        var input2 = "xx1234567890123456789012345678901234567890xxxx1234567890123456789012345678901234567890xxxx1234567890123456789012345678901234567890xxxx1234567890123456789012345678901234567890xx";

        Console.WriteLine(string.Join("\r\n", GetStuff(input)));

        Console.WriteLine();

        Console.WriteLine(string.Join("\r\n", GetStuff(input2)));

    }

}