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