Ошибка при использовании CONS - Lisp

#|vstavit' sr.arifm. elem. posle pozicii max el-ta|#
(defun average (w)
  (loop for a in w
        sum a into s
        count a into c
        finally (return (float (/ s c)))))
 
(defun mx (list)
   (setq a (CAR list))
   (setq i 0)
   (dolist (el list a)
       (cond ((< a el) 
              (setq a el) ;max el-t
              (setq i (+ i 1)) ;pozicia ego
              ) 
          )
      )
           
)
 
(defun foo (list)
   (setq k (average list))
   (if (= i 1)
      (cons k list)
      (cons (car list) (foo (cdr list) k ) (1-i)))
   )
 
(foo '(1 2 3 4 5))