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