head_tail(Str, Head, Tail) :-
    sub_string(Str, 0, 1, _, Head),
    string_concat(Head, Tail, Str).

iintersecta("", _, _) :-
    !, fail.
iintersecta(AS, BS, Inter) :-
    string_concat(AS, _, BS),
    string_length(AS, L), L >= 4,
    Inter = BS.
iintersecta(AAS, BS, Inter) :-
    head_tail(AAS, A, AS),
    iintersecta(AS, BS, IInter),
    string_concat(A, IInter, Inter). % head_tail(Inter, A, IInter)

intersecta(AS, BS, Inter) :-
    iintersecta(AS, BS, Inter), !.
intersecta(AS, BS, Inter) :-
    iintersecta(BS, AS, Inter), !.