Roli the Drug Addict

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Text.RegularExpressions;
//04. Roli The Coder
namespace RoliTheCoder
{
    class RoliTheCoder
    {
        static void Main(string[] args)
        {
            Dictionary<int, string> eventsIds = new Dictionary<int, string>();
            Dictionary<string, List<string>> events = new Dictionary<string, List<string>>();


            string pattern = @"([0-9]+)\s+#\s*(\w+)\s*";

            Regex rgx1 = new Regex(pattern);
            string command = Console.ReadLine();

            while (command != "Time for Code")
            {
                if (rgx1.IsMatch(command))
                {
                    Match match = rgx1.Match(command);
                    int ID = int.Parse(match.Groups[1].Value.Trim());
                    string eventName = match.Groups[2].Value.Trim();
                    string temp = Regex.Replace(command, @"\s+", "");
                    List<string> people = new List<string>();
                    if (temp.Contains("@"))
                    {
                        int startIndex = temp.IndexOf('@');
                        temp = temp.Substring(startIndex);
                        people = temp.Split(new char[] { '@' }, StringSplitOptions.RemoveEmptyEntries).ToList();
                    }

                    if (eventsIds.ContainsKey(ID))
                    {
                        if (eventsIds[ID] == eventName)
                        {
                            if (events.ContainsKey(eventName))
                            {
                                events[eventName].AddRange(people);
                            }
                            else
                            {
                                events.Add(eventName, people);
                            }
                        }
                    }
                    else
                    {
                        eventsIds.Add(ID, eventName);
                        events.Add(eventName, people);
                    }
                }
                command = Console.ReadLine();
            }


            foreach (var eve in events.OrderByDescending(x => x.Value.Count).ThenBy(z => z.Key))
            {
                Console.WriteLine($"{eve.Key} - {eve.Value.Distinct().Count()}");
                foreach (var person in eve.Value.Distinct().OrderBy(x => x))
                {
                    Console.WriteLine($"@{person}");
                }
            }
        }
    }
}