noPairs (x:y:xs)
    | [x,y] `elem` badPairs = False
    | otherwise             = noPairs (y:xs)
  where badPairs = ["ab", "cd", "pq", "xy"]
noPairs (x:y:xs)
    | [x,y] `elem` badPairs = False
    | otherwise             = noPairs (y:xs)
  where badPairs = ["ab", "cd", "pq", "xy"]
noPairs (x:y:xs)
    | [x,y] `elem` badPairs = False
    | otherwise             = noPairs (y:xs)
  where badPairs = ["ab", "cd", "pq", "xy"]