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namespace TimeMachineSimulator
{
    class Program
    {
        static void Main()
        {
            Console.WriteLine("Welcome to the Time Machine Simulator!");
            TimeMachine machine = new();
            while (true)
            {
                Console.WriteLine("What would you like to do?");
                Console.WriteLine("1. Travel in time");
                Console.WriteLine("2. Show current time");
                Console.WriteLine("3. Show travel history");
                Console.WriteLine("4. Exit");
                string input = Console.ReadLine();
                Console.WriteLine();
                switch (input)
                {
                    case "1":
                        Console.Write("Enter the number of years to travel: ");
                        int years = int.Parse(Console.ReadLine());
                        try
                        {
                            machine.Travel(years);
                            Console.WriteLine("Travel successful.");
                        }
                        catch (TimeMachineException e)
                        {
                            Console.WriteLine(e.Message);
                        }
                        break;
                    case "2":
                        Console.WriteLine("Current time: " + machine.GetCurrentTime());
                        break;
                    case "3":
                        List<DateTime> history = machine.GetTravelHistory();
                        Console.WriteLine("Travel history:");
                        foreach (DateTime time in history)
                        {
                            Console.WriteLine(time);
                        }
                        Console.WriteLine();
                        break;
                    case "4":
                        Console.WriteLine("Thank you for using the Time Machine Simulator! Press any key to exit...");
                        Console.ReadKey();
                        return;
                    default:
                        Console.WriteLine("Invalid input. Please try again.");
                        break;
                }
            }
        }
    }

    public class TimeMachineException : Exception { public TimeMachineException(string message) : base(message){}}

    public class TimeMachine
    {
        private DateTime currentTime;
        private readonly List<DateTime> travelHistory;
        public TimeMachine()
        {
            this.currentTime = DateTime.Now;
            this.travelHistory = new List<DateTime>();
        }
        public void Travel(int years)
        {
            DateTime futureTime = this.currentTime.AddYears(years);
            if (futureTime > DateTime.Now)
            {
                throw new TimeMachineException("Cannot travel to the future!");
            }
            this.currentTime = futureTime;
            this.travelHistory.Add(futureTime);
        }
        public DateTime GetCurrentTime()
        {
            return this.currentTime;
        }
        public List<DateTime> GetTravelHistory()
        {
            return this.travelHistory;
        }
    }
}