:-use_module(library(lists)).
test(W1,W2,K,ADD):-
        sub_atom(W1, ADD, XL, 0, S),
        sub_atom(W2, 0, XL, _, S),
        XL =< K, XL > 0.


szolancfa(K, [W1|L], csucs(W1,RL)):-
        findall(P,
               (select(W2,L,L2),
                test(W1,W2,K,_),
                szolancfa(K, [W2|L2], P)),
                RL).