{-# OPTIONS_GHC -Wno-x-partial #-}

import Aoc
import Data.List ( group, sort )

step :: String -> String
step = concat . concatMap (\cs -> [show $ length cs, [head cs]]) . group

part1 :: String -> (Int, String)
part1 x = (length after40, after40)
    where after40 = iterate step x !! 40

part2 :: p -> String -> Int
part2 _ after40 = length (iterate step after40 !! 10) -- only 10 more needed

main = aocMain' single part1 part2