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

dp = [[0 for _ in range(N + 1)] for _ in range(N)]

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

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