fib(0, 0).
fib(1, 1).
fib(N, Res) :-
	N1 is N - 1,
	N2 is N - 2,
	fib(N1, R1),
	fib(N2, R2),
	Res is R1 + R2.
	
fib(N) :-
	fib(N, X),
	write(X).
	
?-fib(33).