using System;

using System.Text;

public class Program

{

    public static void Main()

    {

        DateTime date = DateTime.Now;//new DateTime(2008, 1, 31); // random date

        int rid = 39;

        int bookingCount = 905;

        var result = new StringBuilder();

        var monthsFirstLettersModified = new char[] { 'J', 'F', 'M', 'A', 'Y', 'U', 'L', 'G', 'S', 'C', 'N', 'D' };

        char monthLetter = monthsFirstLettersModified[date.Month-1];

        var digitsToLetters = new char[] {'X', 'T', 'Z', 'E', 'P', 'V', 'K', 'H', 'B', 'W'};

        string lastTwoDigitsOfYear = date.ToString("yy");

        char firstDigitOfYearAsChar = digitsToLetters[int.Parse(lastTwoDigitsOfYear.Substring(0, 1))];

        char secondDigitOfYearAsChar = digitsToLetters[int.Parse(lastTwoDigitsOfYear.Substring(1, 1))];

        result = result.Append(secondDigitOfYearAsChar) // Notice how second comes first

                       .Append(firstDigitOfYearAsChar)

                       .Append(rid)

                       .Append(monthLetter)

                       .Append(bookingCount + 1);

        result = result.Insert(result.Length - 1, new Random().Next(0, 9)); // Insert a single digit before the last element of current result

        Console.WriteLine(result.ToString());

    }

}