10
7
+---+---+---+---+---+---+---+---+---+---+
|   |                   |               |
+   +---+   +---+---+   +   +---+   +---+
|       |   |       |           |       |
+---+   +   +---+   +---+---+---+---+   +
|       |                   |           |
+   +---+---+---+   +---+---+   +---+   +
|       |       |   |           |   |   |
+---+   +---+   +   +   +---+---+   +   +
|   |       |       |   |   |       |   |
+   +---+   +   +---+   +   +   +   +   +
|       |   |       |   |       |   |   |
+   +   +   +---+---+   +   +---+   +   +
|   |                   |       |       |
+---+---+---+---+---+---+---+---+---+---+
