from itertools import accumulate
from math import inf


def main():
    N = int(input())
    cards = list(map(int, input().split()))

    left_score = []
    for idx in range(0, 2*N, 2):
        left_score.append(cards[idx] - cards[idx+1])

    right_score = reversed(list(map(lambda num: -num, left_score)))

    left_score_partial_sum = list(accumulate(left_score))
    right_score_partial_sum = list(accumulate(right_score))
    right_score_partial_sum.reverse()

    maximum = max(right_score_partial_sum[0], left_score_partial_sum[-1])
    for idx in range(N-1):
        maximum = max(
            maximum,
            left_score_partial_sum[idx] + right_score_partial_sum[idx+1]
        )
    print(maximum)


if __name__ == "__main__":
    main()