编辑代码

(defun k (x y)
    (setf l 0)
    (dolist (n y)
        (if (atom n)
            (if (eq n x)
                (setf l (+ l 1))
                (setf l (+ l 0))
            )
            (setf l (+ l (k x n)))
        )
    )
    l
)