module Main where

import           Text.ParserCombinators.Parsec
import Data.List (sort)
import Control.Monad

data Direction = Upper | Lower

doHalving :: [Direction] -> (Int, Int) -> (Int, Int)
doHalving [] p = p
doHalving (Lower:rest) (l, u) = doHalving rest (l, (u+l) `div` 2)
doHalving (Upper:rest) (l, u) = doHalving rest ((u+l) `div` 2 + 1, u)

findId :: (Int, Int) -> Int
findId (row, col) = row * 8 + col

doValidate :: String -> Int
doValidate s = findId (row, col)
    where row = fst $ flip doHalving (0, 127) $ map readDir (take 7 s)
          col = fst $ flip doHalving (0, 7) $ map readDir (drop 7 s)

readDir :: Char -> Direction
readDir c
  | c `elem` "FL" = Lower
  | otherwise = Upper

main :: IO ()
main = do
    n <- lines <$> readFile "input/05"
    let valids = map doValidate n
        ans1 = maximum valids
    print ans1
    print $ sum [minimum valids .. ans1] - sum valids