from itertools import accumulate

N = int(input())
A = [int(zz) for zz in input().split()]

A = [A[2*i]-A[2*i+1] for i in range(N)]

li_left = [0] + list(accumulate(A))
li_right = list(accumulate(A[::-1]))[::-1] + [0]

ans = 0
for i in range(N+1):
    ans = max(ans,li_left[i]-li_right[i])

print(ans)