A-B-C-D and E-F-G-H
to
A-(B-C)-D and E)-F-G-(H
which gives
A-B-E-F-G-H-C-D
or
A----B
|    |
|    | E-----F
|    | |     |
|    | H-----G
D----C

A----B
|    |
|    E-----F
|          |
|    H-----G
D----C