remove1(Items, Structures1, Structures2) :-
        remove2(Items, [], Structures1, Structures2).
remove2([], _Structures, Structures, Structures).
remove2(Items1, Structures1, Structures2, Structures3) :-
        Items1 = [Item | Items2],
        remove3(Item, Structures1, Structures2, Structures4),
        remove2(Items2, [], Structures4, Structures3).
remove3(_Item, Structures, [], Structures).
remove3(Item2, Structures1, Structures2, Structures3) :-
        Structures2 = [Structure | Structures4],
        Structure = [Item1, Item2],
        change(Item1, Item2, [], Structures4, Structures5),
        remove3(Item1, Structures1, Structures5, Structures3), !.
remove3(Item, Structures1, Structures2, Structures3) :-
        Structures2 = [Structure | Structures4],
	
        append(Structures1, [Structure], Structures5),
        remove3(Item, Structures5, Structures4, Structures3).
change(_Item1, _Item2, Structures, [], Structures).
change(Item1, Item2, Structures1, Structures2, Structures3) :-
        Structures2 = [Structure1 | Structures4],
        Structure1 = [Item2, Item3],
        Structure2 = [Item1, Item3],
        append(Structures1, [Structure2], Structures5),
        change(Item1, Item2, Structures5, Structures4, Structures3).
change(Item1, Item2, Structures1, Structures2, Structures3) :-
        Structures2 = [Structure | Structures4],
        not(Structure = [Item2, _]),
        append(Structures1, [Structure], Structures5),
        change(Item1, Item2, Structures5, Structures4, Structures3).