x x
^ ^
| |
+-+

x x x x
^ ^ ^ ^
| | | |
| +-+ |
+-----+

x x x x x x
^ ^ ^ ^ ^ ^
| | | | | |
| | +-+ | |
| +-----+ |
+---------+

x x x x x x x x
^ ^ ^ ^ ^ ^ ^ ^
| | | | | | | |
| | | +-+ | | |
| | +-----+ | |
| +---------+ |
+-------------+