66.hs

import List (sortBy)

isInteger   :: Rational -> Bool
isInteger x = (toRational (truncate x)) == x
         
isQuad      :: (Floating a, Real a) => a -> Bool
isQuad x    = isInteger (toRational (sqrt x))


findMinX    :: (Floating a, Real a, Enum a) => a -> a
findMinX d  = if (isQuad d) then -1 else (head $ filter goes [2..])
    where
        goes x = isQuad ((x*x-1)/d)

allXs = map (\x -> [findMinX x, x]) [1..1000]

maxim = head $ sortBy (\y x -> compare (head x) (head y)) allXs

main = do
        mapM print allXs
        print maxim