03. House Party

using System;
using System.Collections.Generic;
using System.Linq;

namespace HouseParty
{
    class Program
    {
        static void Main(string[] args)
        {
            int num = int.Parse(Console.ReadLine());
            List<string> guest = new List<string>();

            for (int i = 0; i < num; i++)
            {
                List<string> command = new List<string>(Console.ReadLine().Split());

                if (guest.Contains(command[0]))
                {
                    if (command.Count == 3)
                    {
                        Console.WriteLine($"{command[0]} is already in the list!");
                    }
                    else
                    {
                        guest.Remove(command[0]);
                    }
                }
                else
                {
                    if (command.Count == 3)
                    {
                        guest.Add(command[0]);
                    }
                    else
                    {
                        Console.WriteLine($"{command[0]} is not in the list!");
                    }
                }
            }
            foreach (var item in guest)
            {
                Console.WriteLine(item);
            }
        }
    }
}