#include <fstream>
using namespace std;

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

#define NMAX 100005

int v[NMAX];

int dinamica(int start, int n) {
    int dp[NMAX] = {0};

    dp[start] = v[start] + v[start - 1];
    for (int i = start + 1; i <= n + start - 3; ++i) {
        dp[i] = max(dp[i - 1], max(dp[i - 2], dp[i - 3] + v[i] + v[i - 1]));
    }
    return dp[n + start - 3];
}

int main() {
    int n;
    fin >> n;
    for (int i = 1; i <= n; ++i) {
        fin >> v[i];
    }

    v[n + 1] = v[1];

    int maxim = max(dinamica(2, n), max(dinamica(3, n), dinamica(4, n)));

    fout << maxim;
    return 0;
}