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