; calculate a factorial reecursively
(define (fact1 x)
  (if (= x 0)
    1
    (* x (fact1 (- x 1)))))

; tail reursive version
(define (fact2 x)
  (define (factloop x accum)
    (if (< x 1)
      accum
      (factloop (- x 1) (* accum x))))
  (factloop x 1))

(let ((x (read)))
  (displayln (fact1 x))
  (displayln (fact2 x)))