import qualified Data.Map as Map

data Organ = Heart|Brain|Kidney|Spleen deriving (Show,Eq)

organs :: [Organ]
organs = [Heart,Heart,Brain,Spleen,Spleen,Kidney]

ids :: [Int]
ids = [2,7,13,14,21,24]

organPairs :: [(Int,Organ)]
organPairs = zip ids organs

organCatalog :: Map.Map Int Organ
organCatalog = Map.fromList organPairs

possibleDrawers :: [Int]
possibleDrawers = [1 .. 50]

getDrawerContents :: [Int] -> Map.Map Int Organ -> [Maybe Organ]
getDrawerContents ids catalog = map getContents ids
    where getContents = \id -> Map.lookup id catalog

availableOrgans :: [Maybe Organ]
availableOrgans = getDrawerContents possibleDrawers organCatalog

countOrgan :: Organ -> [Maybe Organ] -> Int
countOrgan organ available = length (filter (\x -> x == Just organ) available)

isSomething :: Maybe Organ -> Bool
isSomething Nothing = False
isSomething (Just _) = True

justTheOrgans :: [Maybe Organ]
justTheOrgans = filter isSomething availableOrgans