(defun rm (e x)
  (if (consp x)
      (if (equal e (car x))
          (cdr x)
          (cons (car x) (rm e (cdr x))))
      nil))

(defun memb (e x)
  (if (consp x)
      (or (equal e (car x))
          (memb e (cdr x)))
      nil))

(defun perm (x y)
  (if (consp x)
      (and (memb (car x) y)
           (perm (cdr x) (rm (car x) y)))
      (not (consp y))))

(defun hm (e x)
  (if (endp x)
      0
      (if (equal e (car x))
          (+ 1 (hm e (cdr x)))
          (hm e (cdr x)))))