mission_3.hs

import Control.Monad

type Bar    = [Int]
type BarLen = Int
type SelectLen = Int
type Damage    = Int


main :: IO ()
main = getLengths  >>= \(rLen,bLen) ->
       getBar bLen >>= \bar         ->
       print $ criticalDamage bar rLen


getLengths :: IO (BarLen,SelectLen)
getLengths = getLine >>=
             return . map read . words >>= \(x:y:_) ->
             return (x,y)


getBar :: BarLen -> IO Bar
getBar n = replicateM n getLine >>= return . map read


criticalDamage :: Bar -> SelectLen -> Damage
criticalDamage xs n = foldr max 0 $ damages xs n
  where
    damages ys m = foldr (\a b -> fst a + snd a : b) [] $ zip ys (tail ys)