#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("oo.in");
ofstream fout("oo.out");
#define MAX 100010

int n, i, a[MAX], dp[MAX], best;

void do_alg(int st, int dr)
{
    for(; st <= dr ; st++)
    {
        dp[st] = max(dp[st - 1], a[st] + a[st - 1] + dp[st - 3]);
    }
}

int main()
{
    fin >> n;
    for(i = 1 ; i <= n ; i++)
    {
        fin >> a[i];
    }
    dp[1] = -1000000;
    dp[2] = a[1] + a[2];
    dp[3] = dp[2];
    dp[4] = dp[3];
    do_alg(5, n);
    best = dp[n - 1];
    dp[1] = a[1] + a[n];
    dp[2] = dp[1];
    dp[3] = dp[2];
    do_alg(4, n - 2);
    best = max(best, dp[n - 2]);
    dp[0] = dp[1] = dp[2] = 0;
    do_alg(3, n);
    best = max(best, dp[n]);
    fout << best << "\n";
}