List<long> stones = new List<long>();
public void Input(IEnumerable<string> lines)
{
  stones = string.Concat(lines).Split(' ').Select(v => long.Parse(v)).ToList();
}

public void Part1()
{
  var expanded = TryExpand(stones, 25);

  Console.WriteLine($"Stones: {expanded}");
}
public void Part2()
{
  var expanded = TryExpand(stones, 75);

  Console.WriteLine($"Stones: {expanded}");
}

public long TryExpand(IEnumerable<long> stones, int steps)
{
  if (steps == 0)
    return stones.Count();
  return stones.Select(s => TryExpand(s, steps)).Sum();
}
Dictionary<(long, int), long> cache = new Dictionary<(long, int), long>();
public long TryExpand(long stone, int steps)
{
  var key = (stone, steps);
  if (cache.ContainsKey(key))
    return cache[key];

  var result = TryExpand(Blink(stone), steps - 1);
  cache[key] = result;
  return result;
}

public IEnumerable<long> Blink(long stone)
{
  if (stone == 0)
  {
    yield return 1;
    yield break;
  }
  var str = stone.ToString();
  if (str.Length % 2 == 0)
  {
    yield return long.Parse(str[..(str.Length / 2)]);
    yield return long.Parse(str[(str.Length / 2)..]);
    yield break;
  }
  yield return stone * 2024;
}