N = int(input())
A = list(map(int, input().split()))
lft = [0]
rgt = [0]
for i in range(N):
    lft.append(lft[-1] + A[i*2] - A[i*2+1])
    rgt.append(rgt[-1] + A[-i*2-1] - A[-i*2-2])
ans = 0
for i in range(N+1):
    ans = max(ans, lft[i] + rgt[-i-1])
print(ans)