:- module(fibonacci, _, []).

fib(0, 0) :- !.
fib(1, 1) :- !.
fib(N, F) :-
    N > 1,
    N1 is N-1, N2 is N-2,
    fib(N1, F1), fib(N2, F2),
    F is F1+F2.

:- fib(10, X), write(X), nl.