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