  +----------+ 
  |    x     | 
  |          | 
  +----------+ 
     | |   |   
 +---+ |   +--+
 |     |      |
 |   okay     |
 |     |      |
 v     v      |
+------+      |
|  y   |      |
|      |      |
+------+      |
       |      |
       |  +---+
       |  |    
       v  v    
    +------+   
    |  z   |   
    |      |   
    +------+   
