1 (define (fib n)
2   (fib-iter 1 0 0 1 n))
3 (define (fib-iter a b p q count)
4   (cond ((= count 0) b)
5 	((even? count) (fib-iter a
6 				 b
7 				 (+ (* 2 q p) (square q))
8 				 (+ (square q) (square p))
9 				 (/ count 2)))
10 	(else (fib-iter (+ (