#include <fstream>
#include <algorithm>

using namespace std;

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

const int Nmax = 100005;

int n, maxim;
int v[Nmax], dp[Nmax];

int main()
{
    in >> n;

    for (int i = 1; i <= n; i++)
        in >> v[i];

    dp[2] = dp[3] = dp[4] = v[1] + v[2];

    for (int i = 5; i < n; i++)
    {
        dp[i] = max(dp[i - 1], dp[i - 3] + v[i - 1] + v[i]);
        maxim = max (maxim, dp[i]);
    }

    ///////////////////////////

    dp[1] = dp[2] = 0;

    for (int i = 3; i <= n; i++)
    {
        dp[i] = max(dp[i - 1], dp[i - 3] + v[i - 1] + v[i]);
        maxim = max (maxim, dp[i]);
    }

    ///////////////////////////

    dp[1] = dp[2] = dp[3] = v[n] + v[1];

    for (int i = 4; i < n - 1; i++)
    {
        dp[i] = max(dp[i - 1], dp[i - 3] + v[i - 1] + v[i]);
        maxim = max (maxim, dp[i]);
    }

    out << maxim;
    return 0;
}