; McCarthy's from LISP
(define (samefringe tree1 tree2)
  (or (eq? tree1 tree2)
      (and (pair? tree1) (pair? tree2)
           (same (gopher tree1) (gopher tree2)))))

(define (same x y)
  (and (eq? (car x) (car y))
       (samefringe (cdr x) (cdr y))))

(define (gopher tree)
  (cond ((not (pair? (car tree))) tree)
        (#t (gopher (cons (caar tree)
                         (cons (cdar tree) 
                               (cdr tree)))))))

; 33 paren pairs