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