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

#define nmax 100002

int v[nmax], dp[nmax];
int main()
{
    int i, n;
    ifstream f("oo.in");
    ofstream g("oo.out");
    f >> n;
    for (i = 1; i <= n; ++i)
        f >> v[i];
        dp[n] = v[n] + v[1];
     for (i = 1; i < n; ++i)
        dp[i] = v[i] + v[i + 1];

        dp[1] = max(dp[n], dp[n - 2]);
        dp[2] = max(dp[1], dp[n - 1] + dp[2]);
        dp[3] = max(dp[2], dp[n] + dp[3]);
        int sol = 0;
        for (i = 4; i < n - 2; ++i) {
            dp[i] = max(dp[i - 1], dp[i - 3] + dp[i]);
            if (dp[i] > sol) sol = dp[i];
        }
        g << sol;

    return 0;
}