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