#include <bits/stdc++.h>
using namespace std;
ifstream fin ("oo.in");
ofstream fout ("oo.out");
const int Nmax = 100005;
int a[Nmax] , n;
int dp[Nmax];
int main()
{
    int sol;
    fin >> n;
    for(int i = 1 ; i <= n ; i++)
        fin >> a[i];
    dp[1] = a[1];
    dp[2] = dp[1] + a[2];
    dp[3] = max(dp[2] , a[2] + a[3]);
    for(int i = 3 ; i < n ; i++)
    {
        dp[i] = a[i - 1] + a[i] + dp[i - 3];
        dp[i] = max(dp[i] , dp[i - 1]);
    }
    sol = dp[n - 1];
    dp[1] = 0;
    dp[2] = a[2];
    dp[3] = dp[2] + a[3];
    for(int i = 4 ; i <= n ; i++)
    {
        dp[i] = a[i - 1] + a[i] + dp[i - 3];
        dp[i] = max(dp[i] , dp[i - 1]);

    }
    dp[1] = a[n] + a[1];
    dp[2] = max(dp[1] , a[2] + a[1]);
    dp[3] = max(dp[2] , a[3] + a[4]);
    for(int i = 4 ; i <= n - 2 ; i++)
    {
        dp[i] = a[i - 1] + a[i] + dp[i - 3];
        dp[i] = max(dp[i] , dp[i - 1]);
    }
    sol = max(sol , dp[n - 2]);
    fout << sol << "\n";
    fin.close();
    fout.close();
    return 0;
}