using System;

public class Program

{

    public static void Main()

    {

            Console.WriteLine("Enter the book code of length 18");

            string bookCode = Console.ReadLine();

            Console.WriteLine("----------------------------------");

            if (bookCode.Length == 18)

            {

                if(bookCode.Substring(0,3) == "101" || bookCode.Substring(0,3) == "102" || bookCode.Substring(0,3) == "103")

                    Console.WriteLine("Department Code : {0}", bookCode.Substring(0,3));

                else

                    Console.WriteLine(" Invalid Department Code");

                int year = Convert.ToInt32(bookCode.Substring(3,4));

                if(year>=1900 && year<=2020)

                    Console.WriteLine("Year of Publication : {0}", year);

                else

                    Console.WriteLine("Invalid Year");

                int pages = Convert.ToInt32(bookCode.Substring(7,5));

                if(pages >= 00001 && pages<=99999)

                    Console.WriteLine("Number of Pages : {0}", pages);

                else

                    Console.WriteLine("Invalid Page Numbers");

                char ch = Convert.ToChar(bookCode.Substring(12,1));

                if(Char.IsLetter(ch))

                {

                    if(Char.IsNumber(Convert.ToChar(bookCode.Substring(13,1))) 

                       && Char.IsNumber(Convert.ToChar(bookCode.Substring(14,1))) 

                       && Char.IsNumber(Convert.ToChar(bookCode.Substring(15,1))) 

                       && Char.IsNumber(Convert.ToChar(bookCode.Substring(16,1))) 

                       && Char.IsNumber(Convert.ToChar(bookCode.Substring(17,1))))

                    {

                        Console.WriteLine("Book ID : " + bookCode.Substring(12,6));

                    }

                } else

                {

                    Console.WriteLine("Invalid Book ID");

                }

            }

            else

                Console.WriteLine("Invalid Book Code");

        }

    }

​