N = int(input())
V = list(map(int, input().split()))
dp1 = [0]*N
dp2 = [0]*N
if len(V) == 1:
	print(V[0])
	exit()
dp1[0] = V[0]
dp1[1] = V[0]
dp2[1] = V[1]
for i in range(2, N):
	dp1[i] = max(V[i] + max(dp1[:i-1]), dp1[i-1])
	dp2[i] = max(V[i] + max(dp2[:i-1]), dp2[i-1])

print(max(max(dp1), max(dp2)))