ll isSpace x = x : x' : addSubTitles xs
  | otherwise = x : ("#" ⊕ x' ⊕ "#") : addSubTitles xs
addSubTitles (x:xs) = x : addSubTitles 
addSubTitles (x:x'@('#':_):xs)
  | all isSpace x = x : x' : addSubTitles xs
  | otherwise = x : ("#" ⊕ x' ⊕ "#") : addSubTitles xs
addSubTitles (x:x'@('#':_):xs)
  | all isSpace x = x : x' : addSubTitles xs
  | otherwise = x : ("#" ⊕ x' ⊕ "#") : addSubTitles xs