n = int(input())
a = list(map(int, input().split()))
A = [a[i] - a[i+1] for i in range(0, n*2, 2)]

left = [0] * (n+1)
right = [0] * (n+1)

for i in range(n):
    left[i+1] = left[i] + A[i]

for i in range(n-1, -1, -1):
    right[i] = right[i+1] + A[i]

ans = 0
for i in range(n+1):
    ans = max(ans, left[i] - right[i])

print(ans)