(define not (x)
  (if x
      ()
    t))
(define 1- (x) (- x 1))
(define tak (x y z)
  (if (not (< y x))
      z
    (tak
     (tak (1- x) y z)
     (tak (1- y) z x)
     (tak (1- z) x y))))
(tak 12 6 0)
