+---+     +---+
| B | <## | A |
+---+     +---+
  #         #
  #         #
  v         v
+---+     +---+
| C |     | F |
+---+     +---+
  #         #
  #         #
  v         v
+---+     +---+
| D |     | G |
+---+     +---+
  #         #
  #         #
  v         v
+---+     +---+
| E |     | H |
+---+     +---+
            #
            #
            v
          +---+
          | I |
          +---+