using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var undoStack = new Stack<string>();

        var redoStack = new Stack<string>();

        var text = "";

        while(true)

        {

            Console.Write(">");

            var command = Console.ReadLine().Trim();

            switch(command)

            {

                    case"undo":

                    if(undoStack.Count>0){

                        redoStack.Push(text);

                        text = undoStack.Pop();

                        Console.WriteLine("undone");

                        Console.WriteLine(text);

                    }

                    else{

                        Console.WriteLine("Nothing to undo");

                    }

                    break;

                case "redo":

                    if(redoStack.Count > 0){

                        undoStack.Push(text);

                        text = redoStack.Pop();

                        Console.WriteLine("Redone");

                        Console.WriteLine(text);

                    }

                    else{

                        Console.WriteLine("Nothing to redo");

                    }

                    break;

                default:

                    undoStack.Push(text);

                    redoStack.Clear();

                    text = command;

                    Console.WriteLine("Text is now: " + text);

                    break;

            }

        }

    }

}