#include <fstream>
using namespace std;
ifstream in("oo.in");
ofstream out("oo.out");
const int lim=1e5+3;
int v[lim];
bool f[lim];
int main()
{
    ios_base::sync_with_stdio(false);
    in.tie(0),out.tie(0);
    int n;
    in>>n;
    for(int i=1;i<=n;++i)
        in>>v[i];
    v[n+1]=1;
    for(int i=1;i<=n;++i)
        v[i]+=v[i+1];
    int p=1;
    for(int i=1;i<=n;++i)
        p*=2;
    int maxx=-1;
    for(int j=1;j<=p-1;++j)
    {
        int sum=0;
        int kk=j;
        for(int i=1;i<=n;++i)
        {
            f[i]=kk%2;
            kk/=2;
        }
        f[n+1]=f[1];
        f[n+2]=f[2];
        bool ok=0;
        for(int i=1;i<=n and ok==0;++i)
        if(f[i]==1 and (f[i+1]==1 or f[i+2]==1))
            ok=1;
        if(ok==0)
            for(int i=1;i<=n;++i)
            if(f[i]==1)
            sum+=v[i];
        if(sum>maxx)
            maxx=sum;
    }
    out<<maxx;
    return 0;
}