20
12
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|       |               |               |               |   |               |   |
+   +---+   +---+   +---+   +   +---+---+   +---+---+---+   +   +---+---+---+   +
|           |   |           |           |           |   |   |   |               |
+   +---+---+   +---+---+---+   +---+   +   +---+---+   +   +   +   +   +---+   +
|           |   |       |       |   |   |   |           |   |       |   |       |
+   +---+   +   +   +   +   +---+   +   +   +   +   +---+   +   +---+   +---+---+
|       |       |   |   |           |   |       |               |   |       |   |
+---+---+   +   +---+   +---+---+   +   +   +---+---+---+---+---+   +---+---+   +
|   |       |               |       |               |           |       |   |   |
+   +   +   +   +   +---+---+---+---+   +---+---+---+---+   +---+---+   +   +   +
|   |   |   |   |               |                                       |       |
+   +   +---+---+   +   +---+   +   +---+---+---+---+---+---+   +   +---+   +   +
|   |           |   |   |       |   |                       |   |           |   |
+   +   +   +   +   +   +---+---+---+---+   +   +   +---+   +   +---+   +---+---+
|       |   |   |   |       |   |       |   |   |   |   |   |       |           |
+   +   +---+---+   +---+---+   +---+   +   +---+   +   +   +---+   +   +---+   +
|   |           |               |               |       |   |       |       |   |
+   +   +---+   +   +---+---+   +   +---+   +---+---+---+   +   +   +---+   +---+
|   |       |   |       |       |   |               |       |   |       |   |   |
+   +---+---+---+---+---+---+   +   +---+---+   +---+---+   +   +   +   +   +   +
|   |   |   |               |   |   |       |   |       |   |   |   |   |       |
+   +   +   +---+   +---+   +   +   +---+   +   +---+   +---+---+   +---+   +---+
|               |   |                       |                   |       |       |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
