using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

namespace _01.ParkingLot
{
    class Program
    {
        static void Main(string[] args)
        {
            HashSet<string> parkingLot = new HashSet<string>();
            var input = Regex.Split(Console.ReadLine(),", ");
            while(input[0] != "END")
            {
                if(input[0] == "IN")
                {
                    parkingLot.Add(input[1]);
                }
                else
                {
                    parkingLot.Remove(input[1]);
                }
                input = Regex.Split(Console.ReadLine(), ", ");
            }
            if (parkingLot.Count() == 0)
            {
                Console.WriteLine("Parking Lot is Empty");
            }
            foreach(var ch in parkingLot)
            {
                Console.WriteLine(ch);
            }
        }
    }
}