(defun count_items (lst)
    (cond ((null lst) 0)
          ((atom lst) 1)
          (t (+ 1 (count_items (cdr lst))))
    )
)

(defun findat (l k)
  (cond
    ((atom l) '())
    ((= k 0) (remove-if (complement #'atom) l))
    (t (mapcan #'(lambda (l)
                   (findat l (1- k)))
               l))))

(defun count_level (arb k)
    (count_items (findat arb k))
)

(print (count_level '(a (b (g)) (c (d (e)) (f))) 2))