+---+
| E |
+---+
  ^
  |
  |
  |
  |        +---+
  +----+-> | B |
       |   +---+
       |
       |
       |
       |   +---+
       +-> | C |
       |   +---+
       |
       |
       |
       |   +---+
       +-> | D |
           +---+