/* 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 := 0;
	var b := 1;
	var c := x;
	while not (x < 2)
	do
		c := a-(0-b);
		a := b;
		b := c;
		x := x-1;
	end;
	return c;
end;