-- i found out that intersect exists so i redid day 3

import Data.Char
import Data.List
import GHC.Utils.Misc

getCharPriority c
  | isLower c = fromEnum c - 96
  | isUpper c = fromEnum c - 64 + 26
  | otherwise = undefined

findDuplicate :: [String] -> Char
findDuplicate [l1, l2, l3] = only $ l1 `intersect` l2 `intersect` l3
findDuplicate _ = undefined

main = interact $
  show . sum
  . map (getCharPriority . findDuplicate)
  . chunkList 3
  . lines