#include <bits/stdc++.h>

using namespace std;

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

int n, v[100005], dp[100005][3];

int solve(int index, int lungime)
{
    if (index + 1 > lungime) return 0;
    if (index == 1)
    {
        return max(solve(index + 1, lungime), solve(index + 3, n - 1) + v[index] + v[index + 1]);
    }
    else if (index == 2)
    {
        return max(solve(index + 1, lungime), solve(index + 3, n) + v[index] + v[index + 1]);
    }
    return max(solve(index + 1, lungime), solve(index + 3, lungime) + v[index] + v[index + 1]);
}

int main()
{
    fin >> n;
    for (int i = 1; i <= n; ++i)
        fin >> v[i];
    v[n + 1] = v[1];
    for (int i = n + 1; i >= 1; --i)
    {
        for (int j = 2; j >= 0; --j)
        {
            int nr = n - j + 1;
            if (i + 1 > nr) continue;
            if (i == 1)
            {
                dp[i][j] = max(dp[i + 1][j], v[i] + v[i + 1] + dp[i + 3][2]);
                //return max(solve(index + 1, lungime), solve(index + 3, n - 1) + v[index] + v[index + 1]);
            }
            else if (i == 2)
            {
                dp[i][j] = max(dp[i + 1][j], v[i] + v[i + 1] + dp[i + 3][1]);
                //return max(solve(index + 1, lungime), solve(index + 3, n) + v[index] + v[index + 1]);
            }
            else
            {
                dp[i][j] = max(dp[i + 1][j], v[i] + v[i + 1] + dp[i + 3][j]);
                //return max(solve(index + 1, lungime), solve(index + 3, lungime) + v[index] + v[index + 1]);
            }
        }
    }
    fout << dp[1][0] << "\n";
    return 0;
}