#include <fstream>
#include <cstring>
using namespace std;

ifstream fin("oo.in");
ofstream fout("oo.out");

const int nmax = 100000;
int n;
int d[nmax + 5];
int v[nmax + 5];
int bst;


int solve(int start)
{
    memset(d,0,sizeof(d));
    for(int i=1+start;i<n+start-1;i++)
        if(i<2) d[i]=max(d[i-1],v[i-1]+v[i]);
        else    d[i]=max(d[i-1],d[i-3]+v[i-1]+v[i]);
    return d[n+start-2];
}

int main()
{
    fin>>n;
    for(int i=1;i<=n;i++)   fin>>v[i];
    v[n+1]=v[1];
    fout<<max(solve(1),max(solve(2),solve(3)));

}