#include <fstream>

using namespace std;
const int NMAX=100002;
int v[NMAX], d[NMAX], n, i, j, ans, pos;
int main()
{
    ifstream in("oo.in");
    ofstream out("oo.out");
    in>>n;
    for(i=1; i<=n; ++i)
        in>>v[i];
    v[n+1]=v[1];
    for(i=1; i<=4; ++i)
    {
        int pos=n-2+i;
        d[i]=0;
        d[i+1]=v[i]+v[i+1];
        for(j=i+2; j<=pos; ++j)
            d[j]=max(d[j-1], d[j-3]+v[j]+v[j-1]);
        ans=max(ans,d[pos]);
    }
    out<<ans<<'\n';
    return 0;
}