N = int(input())

V = list(map(int, input().split()))
ab = [[0, 0] for i in range(N)]
ab[0][0] = V[0]

for i in range(1, N):
	ab[i][0] = ab[i - 1][1] + V[i]
	ab[i][1] = max(ab[i - 1][0], ab[i - 1][1])

print(max(ab[N - 1][0], ab[N - 1][1]))