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