% | 1 | 2 | 3 |
% | 4 | 5 | 6 |
% | 7 | 8 | 9 |

queen(1,2).
queen(1,4).
queen(1,5).
queen(2,3).
queen(2,4).
queen(2,5).
queen(2,6).
queen(3,5).
queen(3,6).
queen(4,5).
queen(4,7).
queen(4,8).
queen(5,6).
queen(5,7).
queen(5,8).
queen(5,9).
queen(6,8).
queen(6,9).
queen(7,8).
queen(8,9).

queenbi(X,Y):-queen(X,Y);
              queen(Y,X).

move_user(X,Y) :- retractall(visited(Z)),
	          asserta(visited(X)),
	          asserta(visited(Y)),
	          move(X,Y).

move(X,Y) :- queenbi(X,Y).
move(X,Y) :- queenbi(X,Z),
             not(visited(Z)),
	     asserta(visited(Z)),
	     print(Z),nl,
	     move(Z,Y).