#include <iostream>
#include <fstream>

using namespace std;
ifstream in("oo.in");
ofstream out("oo.out");

int profit[100001], p[100001], n;

int main()
{
    in>>n;
    for(int i=1;i<=n;i++){
        in>>p[i];
    }
    p[n+1]=p[1];
    p[n+2]=p[2];

    for(int i=2;i<=n;i++){
        if(i-3>0){
            profit[i]=max(profit[i-1], p[i]+p[i-1]+profit[i-3]);
        }else{
            profit[i]=max(profit[i-1], p[i]+p[i-1]);
        }


    }
    out<<profit[n-1];
}