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