before Tree
 before -> Tree, l, Label 
at a Label ----  before Label
   after Label
  after -> Tree, l, Label 
 before -> Tree, left, Tree 
  before Tree
   before -> Tree, l, Label 
at a Label ----    before Label
     after Label
    after -> Tree, l, Label 
   before -> Tree, left, Tree 
    before Tree
     before -> Tree, l, Label 
at a Label ----      before Label
       after Label
      after -> Tree, l, Label 
     before -> Tree, right, Tree 
      before Tree
       before -> Tree, l, Label 
at a Label ----        before Label
         after Label
        after -> Tree, l, Label 
       after Tree
      after -> Tree, right, Tree 
     after Tree
    after -> Tree, left, Tree 
   before -> Tree, right, Tree 
    before Tree
     before -> Tree, l, Label 
at a Label ----      before Label
       after Label
      after -> Tree, l, Label 
     after Tree
    after -> Tree, right, Tree 
   after Tree
  after -> Tree, left, Tree 
 after Tree

: Tree  (
at a Label ----	<l> : Label  ( )
	<left> : Tree  (
at a Label ----		<l> : Label  ( )
		<left> : Tree  (
at a Label ----			<l> : Label  ( )
			<right> : Tree  (
at a Label ----				<l> : Label  ( ) ) )
		<right> : Tree  (
at a Label ----
done: result = 13,13
 show left trees 
: Tree  (
	<left> : Tree  (

 show all trees 
: Tree  (
	<left> : Tree  (
		<left> : Tree  (
			<right> : Tree  ( ) )