static void Hashset()
        {
            HashSet<string> quizWords = new HashSet<string>();
            for (int i = 0; i < 10; i++)
            {
                Console.Write("Please type a word: ");
                string word = Console.ReadLine();
                if (quizWords.Contains(word))
                {
                    Console.Write("Error: Word already added. ");
                }
                else
                {
                    quizWords.Add(word);
                    Console.Write("Word added. ");
                }
            }

            Console.Clear();

            while (quizWords.Count > 0)
            {
                Console.Write("Guess a word: ");
                string guess = Console.ReadLine();

                if (quizWords.Contains(guess))
                {
                    quizWords.Remove(guess);
                    Console.WriteLine($"Correct \"{guess}\" removed");
                }
                else
                {
                    Console.WriteLine("Word not found. Try again.");
                }
                Console.WriteLine();
            }
            Console.WriteLine("All words guessed. Congratulations.");
        }