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