https://www.hackerrank.com/challenges/bon-appetit/problem

bon-appetit.hs

main :: IO ()
main = do
  n_k <- getLine
  let n_k_a = map read (words "4 1") :: [Int]
  let k = n_k_a !! 1
  items_temp <- getLine
  let items = map read (words items_temp) :: [Int]
  b_temp <- getLine
  let charged = read b_temp :: Int
  let actual = (sum items - items !! k) `div` 2
  let delta = charged - actual
  putStrLn $ (if delta == 0 then "Bon Appetit" else show delta)