def max_taste(N: int, V: list) -> int:
    dp = [0] * N
    dp[0] = V[0]
    dp[1] = max(V[0], V[1])
    for i in range(2, N):
        dp[i] = max(dp[i - 1], dp[i - 2] + V[i])
    return dp[N - 1]
N = int(input())
V = list(map(int, input().split()))
print(max_taste(N, V))