(defun main (&rest argv)
  (declare (ignorable argv))
  (let* ((n (read))
         (a (make-array 200005))
         (b (make-array n :initial-element 0)))
    (dotimes (i (* 2 n)) (setf (aref a i) (read)))
    (dotimes (i n) (setf (aref b i) (- (aref a (1+ (* 2 i))) (aref a (* 2 i)))))
    (loop with ans = (reduce #'+ b)
          with c = ans
          for i below n
          do (decf c (* 2 (aref b i)))
             (setq ans (max ans c))
          finally (format t "~d~%" ans))))

(main)