#include <fstream>
std::ifstream f("oo.in");
std::ofstream g("oo.out");
const int MAX = 1e5;
void solve(int, int, int&, int[], int[]);
int main() {
    int N;
    f >> N;
    int v[MAX + 5];
    for (int i = 1; i <= N; ++i)
        f >> v[i];
    int dynamic[MAX + 5];
    int max = 0;
    v[N + 1] = v[1];
    solve(1, N - 1, max, v, dynamic);
    solve(2, N, max, v, dynamic);
    solve(3, N + 1, max, v, dynamic);
    g << max << "\n";
    return 0x0;
}
void solve(int start, int end, int& max, int v[], int dynamic[]) {
    dynamic[start] = 0;
    dynamic[start + 1] = v[start] + v[start + 1];
    for (int i = start + 2; i <= end; ++i)
        dynamic[i] = std::max(dynamic[i - 1], dynamic[i - 3] + v[i - 1] + v[i]);
    max = std::max(max, dynamic[end]);
}