import qualified Data.Map.Strict as M

blinkStone :: (Int, Int) -> [(Int, Int)]
blinkStone (0, n) = [(1, n)]
blinkStone (s, n) = let ss = show s
                        nDigit = length ss
                    in  if even nDigit
                            then zip (map read [take (nDigit `div` 2) ss, drop (nDigit `div` 2) ss]) [n, n]
                        else [(s * 2024, n)]

blink :: Int -> M.Map Int Int -> M.Map Int Int
blink 0 m = m
blink n m = blink (n - 1) $ M.fromListWith (+) $ concatMap blinkStone $ M.toList m

main = do
    contents <- M.fromListWith (+) . flip zip (repeat 1) . map read . words <$> readFile "day11.txt"
    print . M.foldl (+) 0 $ blink 75 contents