/* fibonacci */

/* F_0 = 0 */
/* F_1 = 1 */
/* F_n = F_{n-1} + F_{n-2} */

method fib(x)
	if x < 2 then return x; end;
	var a := fib(x-1);
	var b := fib(x-2);
	return a-(0-b);
end;