using System; namespace aoc2019 { class Program { static void Main(string[] args) { if (args.Length == 1 && int.TryParse(args[0], out int daynum)) { if (daynum >= 0 && daynum <= 25) { Day day = DayFactory.GetDay(daynum); day.AllParts(); } else { Console.WriteLine($"{daynum} is an invalid day"); return; } } else { for (var i = 1; i <= 25; ++i) { var day = DayFactory.GetDay(i); if (day == null) continue; Console.WriteLine($"Day {i}:"); day.AllParts(); } } } } }