public void CancelTicket()
        {

            int num = 0;
            do
            {
                try
                {
                    Console.Write("Write the Flight Number : ");
                    num = int.Parse(Console.ReadLine());
                    if (num > 10 || num < 0)
                    {
                        Console.Write("Write the Flight Number : ");
                        num = int.Parse(Console.ReadLine());
                    }

                }
                catch (FormatException e)
                {
                    Console.WriteLine(e.Message);
                    Console.Write("Write the Flight Number : ");
                    num = int.Parse(Console.ReadLine());
                }
            } while (num > 10 || num < 0);


            Console.Write("Write the seat number : ");
            string seat = Console.ReadLine().ToUpper();
            Console.Write("Are you sure you want to cancel this ticket?[yes/no] : ");

            string conf = Console.ReadLine().ToLower();
            if (conf =="yes")
            {
                string[,] seats = new string[6, 5];
                string[] ch = { "A", "B", "C", "D", "E", "F" };
                for (int i = 0; i < 6; i++)
                {
                    for (int y = 0; y < 5; y++)
                    {
                        int n = y + 1;
                        seats[i, y] = (ch[i] + n.ToString());
                    }
                }
                TextReader tr = new StreamReader("Plane" + num + ".txt");
                string[] seatLines = new string[6];
                for (int i = 0; i < 6; i++)
                {
                    seatLines[i] = tr.ReadLine();
                }
                for (int i = 0; i < 6; i++)
                {
                    string[] temp = seatLines[i].Split(default(string[]), StringSplitOptions.RemoveEmptyEntries);
                    for (int y = 0; y < 5; y++)
                    {
                        if (seat == seats[i, y])
                            seats[i, y] = seat;
                        else
                            seats[i, y] = temp[y];
                    }
                }
                tr.Dispose();
                tr.Close();
                TextWriter tw = new StreamWriter("Plane" + num + ".txt");
                StringBuilder sb = new StringBuilder();
                for (int i = 0; i < 6; i++)
                {
                    for (int y = 0; y < 5; y++)
                    {
                        sb.Append(seats[i, y] + " ");
                    }
                    tw.WriteLine(sb.ToString());
                    sb.Clear();
                }

                tw.Dispose();
                tw.Close();
                File.Delete(User.temp + "Ticket" + num + seat + ".txt");
            }
            else { return; }
            Console.Clear();
        }