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