+---+
| A | -+
+---+ |
| |
| |
| |
+---+ |
| B | |
+---+ |
| |
| |
| |
+---+ |
| C | |
+---+ |
| |
| |
| |
+---+ |
| D | -+
+---+
+---+
| A | -+
+---+ |
| |
| |
| |
+---+ |
| B | |
+---+ |
| |
| |
| |
+---+ |
| C | |
+---+ |
| |
| |
| |
+---+ |
| D | -+
+---+