#include <fstream>

using namespace std;

ifstream in ("oo.in");
ofstream out ("oo.out");

const int max_size = 1e5 + 5;

int a[max_size], dp[max_size], n;

int calc_dp (int st, int dr)
{
    dp[st + 1] = a[st] + a[st + 1];
    for (int i = st + 2; i <= dr; i++)
    {
        dp[i] = max(dp[i - 1], dp[i - 3] + a[i - 1] + a[i]);
    //    out << i << " " << dp[i] << '\n';
    }
    int ans = dp[dr];
    for (int i = 1; i <= n + 1; i++)
    {
        dp[i] = 0;
    }
    return ans;
}

int main ()
{
    in >> n;
    for (int i = 1; i <= n; i++)
    {
        in >> a[i];
    }
    a[n + 1] = a[1];
    int ans = calc_dp(1, n - 1);
    ans = max(ans, calc_dp(2, n));
    ans = max(ans, calc_dp(3, n + 1));
    out << ans;
    in.close();
    out.close();
    return 0;
}