Зависает программа LispWorks после запуска данного кода

(print (ableToUse2 1))

(defvar production
 '( 
      (1 10) (1 7) 
      (2 9) (2 11) (2 8)
      (3 10) (3 12) (3 5)
      (4 6) (4 11)
      (5 11) (5 14) (5 3)
      (6 4) (6 12) (6 13) (6 15)
      (7 14) (7 16) (7 1) (7 9) 
      (8 2) (8 10) (8 15)
      (9 15) (9 7) (9 2)
      (10 16) (10 8) (10 1) (10 3)
      (11 2) (11 4) (11 5) (11 13)
      (12 3) (12 6) (12 14)
      (13 6) (13 11) 
      (14 5) (14 7) (14 12)
      (15 6) (15 8) (15 9)
      (16 7) (16 10)
  ))
 
(defun ableToUse (status)
   (mapcan
     #'(lambda (rule)
       (if (eq status (car rule)) (list rule) nil))
         production
))
 
(defun ableToUse2 (status)
  (mapcan 'cdr (ableToUse status))
    
)
 
 
 
 
 
(defun route (currentSt haventBeen lastSt)
 (if (not (eq lastSt (first (ableToUse2 currentSt)))) (defvar nextSt1 (first (ableToUse2 currentSt))) (defvar nextSt1 nil))
 (if (not (eq lastSt (second (ableToUse2 currentSt)))) (defvar nextSt2 (second (ableToUse2 currentSt))) (defvar nextSt2 nil))
 (if (not (eq lastSt (third (ableToUse2 currentSt)))) (defvar nextSt3 (third (ableToUse2 currentSt))) (defvar nextSt3 nil))
 (if (not (eq lastSt (fourth (ableToUse2 currentSt)))) (defvar nextSt4 (fourth (ableToUse2 currentSt))) (defvar nextSt4 nil))
 (cond
   ( (null haventBeen) nil)
   ((member nextSt1 haventBeen) (cons nextSt1 (route nextSt1 (remove nextSt1 haventBeen) currentSt)))
   ((member nextSt2 haventBeen) (cons nextSt2 (route nextSt2 (remove nextSt2 haventBeen) currentSt)))
   ((member nextSt3 haventBeen) (cons nextSt3 (route nextSt3 (remove nextSt3 haventBeen) currentSt)))
   ((member nextSt4 haventBeen) (cons nextSt4 (route nextSt4 (remove nextSt4 haventBeen) currentSt)))
   (t (cons (car (remove lastSt (ableToUse2 currentSt))) (route (car (remove lastSt (ableToUse2 currentSt))) haventBeen currentSt)))))  
 
(print (route 1 '(2 3 4 5 6 7 8 9 10 11 12 13 14 15 16) nil))