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

namespace _05.ParkingValidation
{
    class StartUp
    {
        static void Main()
        {
            int numberOfCommands = int.Parse(Console.ReadLine());
            Dictionary<string, string> parkingRegister = new Dictionary<string, string>();

            for (int i = 0; i < numberOfCommands; i++)
            {
                string[] args = Console.ReadLine().Split(' ');
                string command = args[0];
                string username = args[1];

                if (command == "register")
                {
                    string licensePlate = args[2];
                    string licensePlateNumbers = licensePlate.Substring(2, 4);
                    string licensePlateLetters = licensePlate.Substring(0, 2) + licensePlate.Substring(6);
                    bool isValid = false;
                    if (licensePlate.Length == 8 && int.TryParse(licensePlateNumbers, out int ignor))
                    {
                        foreach (var letter in licensePlateLetters)
                        {
                            isValid = Char.IsLetter(letter) && Char.IsUpper(letter);
                            if (!isValid)
                            {
                                break;
                            }
                        }
                    }
                    if (isValid == true)
                    {
                        if (!parkingRegister.ContainsKey(username))
                        {
                            if (!parkingRegister.ContainsValue(licensePlate))
                            {
                                parkingRegister.Add(username, licensePlate);
                                Console.WriteLine($"{username} registered {licensePlate} successfully");
                            }
                            else
                            {
                                Console.WriteLine($"ERROR: license plate {licensePlate} is busy");
                            }
                        }
                        else
                        {
                            Console.WriteLine($"ERROR: already registered with plate number {parkingRegister[username]}");
                        }
                    }
                    else
                    {
                        Console.WriteLine($"ERROR: invalid license plate {licensePlate}");
                    }
                }
                else if (command == "unregister")
                {
                    if (parkingRegister.ContainsKey(username))
                    {
                        parkingRegister.Remove(username);
                        Console.WriteLine($"user {username} unregistered successfully");
                    }
                    else
                    {
                        Console.WriteLine($"ERROR: user {username} not found");
                    }
                }
            }
            if (parkingRegister.Count > 0)
            {
                Console.WriteLine(string.Join(Environment.NewLine, parkingRegister.Select(u => $"{u.Key} => {u.Value}")));
            }
        }
    }
}