#include <fstream>
using namespace std;
ifstream fin("oo.in");
ofstream fout("oo.out");
int n, sum, maxim, dp[100000], V[100000];
int main()
{
    fin >> n;
    for (int i=1; i<=n; i++) fin >> V[i];
    dp[0] = V[1] + V[n];
    for (int i=1; i<=n-2; i++)
    {
        if (i > 2 && dp[i-3] > maxim) maxim = dp[i-3];
        dp[i] = V[i] + V[i+1] + maxim;
    }

    for (int i=1; i<=n-2; i++) if (dp[i] > maxim) maxim = dp[i];
    fout << maxim << '\n';
    fout.close();
    return 0;
}