(define (cau2 s k m) (let* ((nk (quotient s k)) (nm (* (quotient k m) nk)))
  (if (= nk 0) 0 (+ (cau2 (+ (remainder s k) (* (remainder k m) nk)) k m) nm))))
(with-input-from-file "CAU2.INP" (lambda ()
  (with-output-to-file "CAU2.OUT" (lambda ()
    (format #t "~a\n" (cau2 (read) (read) (read)))))))