(defun generate-dividends (l r ll rr)
  (sort (remove-duplicates
         (loop for i from l to r
               append (loop for j from ll to rr
                            collect (/ i j))))
        #'<))
        
(defun generate-differences (l r ll rr)
  (let ((a (generate-dividends l r ll rr)))
    (sort (remove-duplicates (mapcar #'- (rest a) a))
          #'<)))