static void Main(string[] args)
        {
            try
            {
                if (stringDomainName != null)
                {
                    string[] info = TextProcessing.login();
                    while (true)
                    {
                        if (validateUser(info[0], info[1]))
                        {
                            goto PROCESS;
                        }
                        else
                        {
                            Console.Clear();
                            Console.Write("Invalid username or password. Try Again. (y/n): ");
                            string key = Console.ReadLine().ToUpper();
                            if (key.Equals("Y") || key.Equals("YES"))
                            {
                                info = TextProcessing.login();
                            }
                            else if (key.Equals("N") || key.Equals("NO"))
                            {
                                goto END;
                            }
                        }
                    }
PROCESS:
                    Console.Clear();
                    Console.WriteLine("Welcome!");
                    while (true)
                    {
                        Console.Write("Please select feature:\n[1]Show OU\n[2]Show User\n[3]Show Computer\n[4]Show Groups\n[5]Exit\n:");
                        string choose = Console.ReadLine();
                        switch (choose)
                        {
                        case "1":
                            OU.Clear();
                            OU = getOU();
                            foreach (string nameOU in OU)
                            {
                                Console.WriteLine(nameOU);
                            }
                            break;

                        case "2":
                            Users.Clear();
                            Users = getUsers();
                            foreach (User user in Users)
                            {
                                Console.WriteLine(user.SAMAccountName + " - " + user.commonName + " - " + user.ou);
                            }
                            break;

                        case "3":
                            Computers.Clear();
                            Computers = getComputer();
                            foreach (string computer in Computers)
                            {
                                Console.WriteLine(computer);
                            }
                            break;

                        case "4":
                            Groups.Clear();
                            Groups = getGroup();
                            foreach (string group in Groups)
                            {
                                Console.WriteLine(group);
                            }
                            break;

                        case "5":
                            Console.WriteLine("====================");
                            goto END;

                        default:
                            break;
                        }
                        Console.WriteLine("====================");
                    }
END:
                    Console.WriteLine("Goodbye!");
                }
                else
                {
                    Console.WriteLine("Your computer is not a member of domain");
                }
            }
            catch (Exception e)
            {
                Console.WriteLine(e);
            }
        }