; (define (make-rat n d) (cons n d))
(define (numer x) (car x))
(define (denom x) (cdr x))

(define (make-rat n d)
  (cond ((and (> n 0) (> d 0))
	   (cons n d))
	((and (< n 0) (< d 0))
	   (cons (* n -1) (* d -1)))
	((and (< n 0) (> d 0))
	   (cons n d))
	(else
	   (cons (* n -1) (* d -1)))))