;;;; The TAKeuchi function using lists as counters.
(define (listn n)
  (if (not (= 0 n))
      (cons n (listn (- n 1)))
      '()))

(define l18 (listn 18))
(define l12 (listn 12))
(define l6 (listn 6))

(define (mas x y z)
  (if (not (shorterp y x))
      z
      (mas (mas (cdr x) y z)
           (mas (cdr y) z x)
           (mas (cdr z) x y))))

(define (shorterp x y)
  (and (pair? y) (or (null? x) (shorterp (cdr x) (cdr y)))))
;; call: (mas l18 l12 l6)