#include <fstream>
#include <cstring>
using namespace std;

const int MAX_N = 100005;

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

int N, A[MAX_N], Sol;

int main()
{
    fin >> N;

    for(int i = 1; i <= N; ++i)
        fin >> A[i];
    A[N+1] = A[1], A[N+2] = A[2];

    for(int k = 0; k < 3; ++k)
    {
        int bst[MAX_N];
        memset(bst, 0, sizeof bst);

        for(int i = k+1; i <= N+k; ++i)
        {
            bst[i] = max(bst[i-1], bst[i-2]);
            if(i != k+1)
                bst[i] = max(bst[i], bst[i-3] + A[i] + A[i-1]);
        }

        Sol = max(Sol, bst[N+k-1]);
    }

    fout << Sol;
}