diff([],[], []).
diff(_,[], []).
diff([],_, []).

diff([A|TailA], [B|TailB], [Сomposition|СompositionTail]):-
    Сomposition is A-B, diff(TailA, TailB, СompositionTail).

len([], 0).
len([_|T], L) :- len(T, Y), L is Y + 1.

diff_len([], [], 0).
diff_len(A, B, X) :- diff(A, B, Diff), len(Diff, X).