SottUniParty

namespace SoftUniParty
{
    using System;
    using System.Collections.Generic;

    public class Startup
    {
        private static SortedSet<string> guestList;

        public static void Main()
        {
            guestList = new SortedSet<string>();

            ManageTheGuestList(item => guestList.Add(item), "PARTY");
            ManageTheGuestList(item => guestList.Remove(item), "END");

            Console.WriteLine(guestList.Count);
            Console.WriteLine(string.Join($"{Environment.NewLine}", guestList));
        }

        public static void ManageTheGuestList(Action<string> executeActionOnSortedSet, string endWord)
        {
            string inputLine = Console.ReadLine();
            while (inputLine != endWord)
            {
                executeActionOnSortedSet(inputLine);

                inputLine = Console.ReadLine();
            }
        }
    }
}