Crossing.hs

import Data.List

main = interact $ unlines . map showSolution . zip [1..] . map solve . parseProblems

parseProblems = parse . map (map read . words) . tail . lines
  where parse [] = []
        parse ([n]:xs) = map (\ [x,y] -> (x,y)) (take n xs) : parse (drop n xs)

showSolution (n, s) = "Case #" ++ show n ++ ": " ++ show s

solve xs = sum [ fromEnum $ signum (l1-l2) /= signum (r1-r2) | (l1,r1):ys <- tails xs, (l2,r2) <- ys ]