from itertools import accumulate
N = int(input())
A = list(map(int, input().split()))

memo = []
for i in range(N):
    l, r = A[2*i], A[2*i + 1]
    memo.append(l - r)

# 左から累積
memo_l = list(accumulate(memo, initial=0))

# 右から累積
memo_r = [0]
for i in range(N - 1, -1, -1):
    memo_r.append(memo_r[-1] - memo[i])
memo_r.reverse()

ansl = []
for i in range(N + 1):
    ansl.append(memo_l[i] + memo_r[i])

print(max(ansl))