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

int v[100010],n,i,j,maxim,d[100010];

int main () {

    fin>>n;

    for (i=1;i<=n;i++)
        fin>>v[i];
    v[n+1]=v[1];

    for (i=1;i<=3;i++) {

        for (j=1;j<=i;j++)
            d[j]=0;
        d[i+1]=v[i]+v[i+1];
        for (j=i+2;j<=n-2+i;j++) {
            d[j]=d[j-1];
            if (d[j-3]+v[j-1]+v[j]>d[j])
                d[j]=d[j-3]+v[j-1]+v[j];
        }

        if (d[n-2+i]>maxim)
            maxim=d[n-2+i];
    }

    fout<<maxim<<"\n";

    return 0;
}