static void Main(string[] args) { Box <string> list = new Box <string>(); int n = int.Parse(Console.ReadLine()); for (int i = 0; i < n; i++) { var input = Console.ReadLine(); list.AddElement(input); } var indexes = Console.ReadLine().Split(" ", StringSplitOptions.RemoveEmptyEntries).Select(int.Parse).ToArray(); int firstElement = indexes[0]; int secondElement = indexes[1]; list.SwapElements(firstElement, secondElement); Console.WriteLine(String.Join(Environment.NewLine, list)); }