+-------+
| |
| |
| +--------+
| | |
+-------+ | +-------------+
| | |
+---------> |
| |
+---------+ | |
| | +-------------+
| |
| +---------+
| | |
| | |
+---------+ | +--------------+
| | |
| | |
| | |
+--------> |
| |
+--------------+