(defun main (&rest argv)
  (declare (ignorable argv))
  (let* ((x1 (read))
         (y1 (read))
         (x2 (read))
         (y2 (read)))
    (format t "~d~%" (if (and (> x1 x2) (= x1 y1) (= x2 y2))
                         (1+ x1)
                         (max x1 y1)))))

(main)