Sets & Dictionaries Advanced - 6. Parking Lot

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

namespace Advanced
{
    class Program
    {
        static void Main(string[] args)
        {
            var cars = new HashSet<string>();

            while (true)
            {
                var input = Console.ReadLine();

                if (input == "END")
                {
                    break;
                }

                var line = input.Split(", ");

                var command = line[0];
                var carNumber = line[1];

                switch (command)
                {
                    case "IN":
                        cars.Add(carNumber);
                        break;

                    case "OUT":
                        if (cars.Contains(carNumber))
                        {
                            cars.Remove(carNumber);
                        }
                        break;

                }
            }

            if (cars.Count > 0)
            {
                foreach (var car in cars)
                {
                    Console.WriteLine(car);
                }
            }

            else
            {
                Console.WriteLine("Parking Lot is Empty");
            }
        }
    }
}