|
                   y                          |
                 <++>                         w
                     `--..__                 <0>
                             x         __..-'   \
                            <->    =>  y          x
                      __..-'   \      <0>        <0>
                      w         []       \          \
                     <0>                  [w]        []
                        \
                         [x]