#include <iostream>
#include <fstream>
using namespace std;
ifstream in("oo.in");
ofstream out("oo.out");
int n,v[100050],i,maxim,j,a,b,sol[100050];
int main()
{
    in>>n;
    for(i=1;i<=n;i++)
        in>>v[i];
    v[n+1]=v[1];
    for(j=1;j<=3;j++)
    {
    sol[j] = 0;
    sol[j+1]=v[j]+v[j+1];

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


    if ( sol[j+n-2] >maxim)
        maxim = sol[j+n-2];
    for(i=1;i<=10;i++)
        sol[i]=0;
    }
    out<<maxim;
    in.close();
    out.close();
    return 0;
}