16
9
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|   |   |                       |               |       |       |
+   +   +   +---+---+   +---+   +   +   +---+   +   +---+---+   +
|                   |   |           |       |           |       |
+   +---+---+---+   +   +---+   +---+---+   +   +---+   +   +   +
|               |   |   |       |       |   |       |       |   |
+   +   +   +---+   +---+---+   +   +---+   +---+   +---+   +   +
|   |   |   |       |           |               |   |       |   |
+   +   +---+---+---+   +   +   +   +---+   +   +---+   +---+---+
|   |   |               |   |   |   |       |   |   |           |
+   +   +---+---+   +   +---+---+---+   +---+   +   +   +   +---+
|   |           |   |               |   |       |       |   |   |
+   +   +   +   +   +---+---+---+   +---+---+   +---+---+   +   +
|   |   |   |   |       |           |   |           |   |       |
+---+---+   +   +   +   +---+---+---+   +---+   +   +   +---+   +
|           |   |   |       |       |           |           |   |
+   +---+   +---+---+   +---+---+   +---+---+   +---+   +---+---+
|       |   |                               |       |           |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
