(letrec* ((n (read))
          (m (read))
          (p (read))
          (q (read))
          (r (make-vector 12 1))
          (r-init (lambda (i j)
                          (unless (> i j)
                                  (begin 
                                    (set! (~ r (- i 1)) 2)
                                    (r-init (+ i 1) j)))))
          (check (lambda (rest a)
                         (let1 rest1 
                               (- rest 
                                  (* m 
                                     (~ r (remainder a 12)))) 
                               (if (<= rest1 0)
                                   (+ a 1)
                                   (check rest1 (+ a 1)))))))
         (r-init p (- (+ p q) 1))
         (print (check n 0)))