Write a LISP Program to Count the number of elements in a given list

(a)-> (defun cnt(lt)     # Given list -> (a)
           (setf n 0)
           (loop (if(endp lt)
                  (return n))
                (if(cond((equal 'a(car lt)
            (setf n(+n 1)))
            (set lt(cdr lt))
            )