; tree ::= int | (make-pair tree tree)
; tree -> int
(define-struct pair (left right))
(define (Pi t)
  (cond [(number? t) t]
        [else (* (Pi (pair-left t))
                 (Pi (pair-right t)))]))
(define t1 (make-pair 166 (make-pair 12 24)))
(define (Pi/k1 t k)
  (cond [(number? t) (k t)]
        [else (k (* (Pi (pair-left t))
                 (Pi (pair-right t))))]))
(define id (lambda (x) x))
(define (Pi/k2 t k)
  (cond [(number? t) (k t)]
        [else (Pi/k2 (pair-left t)
                     (lambda (itroc)
                         (k (* itroc 
                               (Pi (pair-right t))))))]))