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