lets
` <*>
  + <*>
  | + pure (\u1 -> (\u2 -> u1))
  | ` <|>
  |   + <*>
  |   | + <*>
  |   | | + pure (\u1 -> (\u2 -> u1))
  |   | | ` pure 'a'
  |   | ` satisfy
  |   ` <*>
  |     + <*>
  |     | + pure (\u1 -> (\u2 -> u1))
  |     | ` pure 'b'
  |     ` satisfy
  ` <*>
    + <*>
    | + pure (\u1 -> (\u2 -> u1))
    | ` pure 'c'
    ` satisfy