import IO
import Char

data BTree a = Node a Int (Maybe (BTree a)) (Maybe (BTree a))

type Dictionary = (Maybe (BTree String))

update newWord dict = case dict of
	Nothing		-> Just (Node newWord 1 Nothing Nothing)
	Just node	-> update' newWord node

update' newWord (Node word count left right)
	| word == newWord = Just (Node word (count + 1) left right)
	| word < newWord  = Just (Node word count left (update newWord right))
	| word > newWord  = Just (Node word count (update newWord left) right)

toList = toList' []

toList' list node = case node of
	Nothing -> list
	Just (Node word count left right) -> toList' ((word, count) : toList' list right) left

isLetter c = isAlphaNum c || c=='\''

normalize = map toLower . filter isLetter

isWord [] = False
isWord s = True

nwords = filter isWord . map normalize . words

wordCount = length . words

wordTotals = toList . foldr update Nothing . nwords

wordFrequency s =
	let	total = (fromIntegral . wordCount) s
		freq = \(word, count) -> (word, (fromIntegral count) / total)
	in
	(map freq . wordTotals) s

format (word, frequency) = show word ++ ": " ++ show frequency 

main = do
	input <- hGetContents stdin
	(mapM (hPutStrLn stdout) . map format . wordFrequency) input