main :: IO ()
main = do
  input <- readFile "input"
  let inList = map parseLine . lines $ input
  let safelist = map isSafeDamp inList
  print (count True safelist)

parseLine = map (read :: String->Int) . words

count x = length . filter (x ==)

sublists xs = [[x | (x,j) <- zip xs [0..], j /= i] | i <- [0..length xs -1]]

isSafeDamp = or . map isSafe . sublists

isSafe levels =
  let diff = zipWith (-) levels (tail levels)
      absdiff = map abs diff
  in (all (> 0) diff || all (< 0) diff) &&
     (minimum absdiff) >= 1 &&
     (maximum absdiff) <= 3