module Main where

main :: IO ()
main = interact translate

translate :: String -> String
translate = inHTML (byWords transWord)

transWord :: String -> String
transWord = reverse

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-- auxiliaries

byWords :: (String -> String) -> String -> String
byWords f s = unwords [f w | w <- words s]

byLines :: (String -> String) -> String -> String
byLines f s = unlines [f w | w <- lines s]

inHTML :: (String -> String) -> String -> String
inHTML f = byLines (inHTMLPlus f)


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---- this will not be explained on the course ------

inHTMLPlus :: (String -> String) -> String -> String
inHTMLPlus f [] = []
inHTMLPlus f ('>':s) = ">" ++ inHTMLPlus f s
inHTMLPlus f s =
  let 
    (s1,s2) = span (/= '<') s
    (s3,s4) = span (/= '>') s2
  in f s1 ++ s3 ++ inHTMLPlus f s4
----------------------------------------------------