Activity Tracker

namespace _13.ActivityTracker
{
    using System;
    using System.Collections.Generic;
    using System.Text.RegularExpressions;

    class ActivityTracker
    {
        static void Main(string[] args)
        {
            int linesCount = int.Parse(Console.ReadLine());

            SortedDictionary<int, SortedDictionary<string, int>> monthsActivity = new SortedDictionary<int, SortedDictionary<string, int>>();
            string pattern = @"\d{2}/(\d{2})/\d{4}\s+(\w{1,20})\s+(\d+)";
            for (int i = 0; i < linesCount; i++)
            {
                string input = Console.ReadLine();
                MatchCollection matches = Regex.Matches(input, pattern);
                int month = 0, distance = 0;
                string username = string.Empty;
                foreach (Match match in matches)
                {
                    month = int.Parse(match.Groups[1].Value);
                    username = match.Groups[2].Value;
                    distance = int.Parse(match.Groups[3].Value);
                }

                if (!monthsActivity.ContainsKey(month))
                {
                    monthsActivity[month] = new SortedDictionary<string, int>();
                }

                if (!monthsActivity[month].ContainsKey(username))
                {
                    monthsActivity[month][username] = 0;
                }

                monthsActivity[month][username] += distance;
            }

            foreach (var monthInfo in monthsActivity)
            {
                Console.Write("{0}: ", monthInfo.Key);
                int count = monthInfo.Value.Count;
                foreach (var userInfo in monthInfo.Value)
                {
                    count--;
                    Console.Write("{0}({1})", userInfo.Key, userInfo.Value);
                    if (count > 0)
                    {
                        Console.Write(", ");
                    }
                }
                Console.WriteLine();
            }
        }
    }
}