#include <fstream>

using namespace std;

ifstream in("oo.in");
ofstream out("oo.out");
int v[100005];
int d[100005];
int n, add;
int ans = 0;

int solve(int start, int end)
{
    
    for(int i = 1; i<=n+1; i++)
    {
        d[i] = 0;
    }
    
    for(int i = start+1; i<=start+end-1; i++)
    {
        add = 0;
        if(i >= 4)
        {
            add = d[i-3];
        }
        d[i] = max(d[i-1], v[i-1] + v[i] + add);
    }
    return d[start+n-2];
}

int main()
{
    in>>n;
    for(int i = 1; i<=n; i++)
    {
        in>>v[i];
    }
    
    v[n+1] = v[1];
    
    ans = max(solve(3, n), solve(1, n));
    ans = max(ans, solve(2, n));
    
    out<<ans;
    

    return 0;
}