type Odds = [Odd]
data Odd = One | Three | Five | Seven | Nine deriving (Eq, Enum, Bounded)
 
one :: Odds
one = [minBound]
 
instance Show Odd where
    show One   = "1"
    show Three = "3"
    show Five  = "5"
    show Seven = "7"
    show Nine  = "9"
 
showOdds :: Odds -> String
showOdds = concatMap show
 
inc :: Odds -> Odds
inc xs = case foldr f ([], True) xs of
    (acc, True) -> minBound : acc
    (acc, _)    -> acc
    where
      f x (acc, True) | x == maxBound = (minBound : acc, True)
                      | otherwise     = (succ x : acc, False)
      f x (acc, _)                    = (x : acc, False)
 
main :: IO ()
main = print . takeWhile (<=1000) . map (read . showOdds) $ iterate inc one
 

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