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