try
` <*>
  + <*>
  | + <*>
  | | + <*>
  | | | + pure (\u1 -> (\u2 -> (\u3 -> (\u4 -> 'a' : ('b' : ('c' : ('d' : Pure)))))))
  | | | ` satisfy
  | | ` satisfy
  | ` satisfy
  ` satisfy