object PartTwo(string input)
{
var origo = new Hex(0, 0, 0);
var locations = input.Lines()
.Select(s => ToHexDirections(s).Aggregate(origo, (a, d) => a.Neighbor(d)))
.ToArray();
var blacks = locations.GroupBy(h => h).Where(g => g.Count() % 2 == 1).Select(g => g.Key);
var exhibit = new Exhibit(blacks);
for (int i = 0; i < 100; i++)
{
exhibit.Next();
Console.Out.WriteLine($"Day {exhibit.Day}: {exhibit.Blacks.Count}");
}
return(exhibit.Blacks.Count);
}