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

namespace _05.Parking_Validation
{
    class Program
    {
        static void Main(string[] args)
        {

            var n = int.Parse(Console.ReadLine());
            var userLicense = new Dictionary<string, string>();

            for (int i = 0; i < n; i++)
            {
                var input = Console.ReadLine();
                var command = input
                    .Split()
                    .ToArray()[0];
                var username = input
                    .Split()
                    .ToArray()[1];

                switch (command)
                {
                    case "register":
                        var license = input
                            .Split()
                            .ToArray()[2];
                        if (!IsValid(license))
                        {
                            Console.WriteLine($"ERROR: invalid license plate {license}");
                            break;
                        }

                        if (userLicense.ContainsKey(username))
                        {
                            Console.WriteLine($"ERROR: already registered " +
                                $"with plate number {userLicense[username]}");
                            break;
                        }

                        if (userLicense.ContainsValue(license))
                        {
                            Console.WriteLine($"ERROR: license plate {license} is busy");
                            break;
                        }

                        userLicense[username] = license;
                        Console.WriteLine($"{username} registered {license} successfully");
                        break;

                    case "unregister":
                        if (!userLicense.ContainsKey(username))
                        {
                            Console.WriteLine($"ERROR: user {username} not found");
                            break;
                        }

                        userLicense.Remove(username);
                        Console.WriteLine($"user {username} unregistered successfully");
                        break;
                }
            }

            foreach (var pair in userLicense)
            {
                Console.WriteLine($"{pair.Key} => {pair.Value}");
            }
        }

        private static bool IsValid(string license)
        {
            string pattern = "([A-Z]{2})([0-9]{4})([A-Z]{2})";
            Regex regex = new Regex(pattern);
            Match match = regex.Match(license);
            return match.Success;
        }
    }
}