merge(A, [], A).
merge([], B, B).
merge([A|RestAs], [B|RestBs], [A|Merged]) :-
    A < B,
    merge(RestAs, [B|RestBs], Merged).
merge([A|RestAs], [B|RestBs], [B|Merged]) :-
    B =< A,
    merge([A|RestAs], RestBs, Merged).