Program to resolve the sokoban problem.
Initial state:
_____________________________
| | | |
| 1 | 2 | 3 |
|_________|_________|_________|
| | | |
| 4 | 5 (B) | 6 (B) |
|_________|_________|_________|
| | | |
| 7 (A) | 8 (G) | 9 (G) |
|_________|_________|_________|
A: Position of the android (robot)
B: Position of a box
G: Position where a box must end.
Tested in macOS High Sierra with Ciao Prolog.