static void Main(string[] args) { if (args.Length > 0) { ICollectionsExercises exercises = null; switch (args[0]) { case "Nikita": exercises = new Nikita.CollectionsExercises(); break; case "Taisiya": exercises = new Nikita.CollectionsExercises(); break; case "Sergey": exercises = new Sergey.CollectionsExercises(); break; case "Tatyana": exercises = new Tatyana.CollectionsExercises(); break; default: Console.WriteLine("Wrong argument. Choose one of: Nikita, Taisiya, Sergey, Tatyana"); break; } if (exercises != null) { exercises.WorkPriorityQueue(); } } }