# No.45 回転寿司
def main():
    N = int(input())
    A = tuple(map(int, input().split()))
    # dp[take or not][i] := optimum value when taking i-th sushi or not
    dp = [[0] * (N + 1) for _ in range(2)]
    for i in range(1, N + 1):
        dp[0][i] = dp[1][i - 1] + A[i - 1]
        dp[1][i] = max(dp[0][i - 1], dp[1][i - 1])
    print(max(dp[0][-1], dp[1][-1]))


if __name__ == "__main__":
    main()