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