
       +---------+
       |         |
       |         |
  +----+----+    |
  |         v    |
+---+     +---+  |
| A |     | C |  |
+---+     +---+  |
  |         ^    |
  +----+----+    |
       |         |
       |         |
       |         |
       |         |
       |  +---+  |
       +> | B | <+
          +---+
