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