import sys

N = int(input())
V = list(map(int, input().split()))

if N <= 2:
	print(max(V))
	exit()

dp = [V[0],V[1]]

for i in range(2, N):
	mx = 0
	for j in range(i - 1):
		vij = V[i] + dp[j]
		if vij > mx:
			mx = vij
	dp.append(mx)
	
print(max(dp))