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