#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 mx[nmax + 5];
int v[nmax + 5];
int bst;

pair<int,int> vec(int x,int y)
{
    int lv=x-1;
    int rv=y+1;
    if(x==1)
        lv = n;
    if(y==n)
        rv = 1;
    return {lv,rv};

}

int main()
{
    fin>>n;
    for(int i=1;i<=n;i++)   fin>>v[i];
    for(int i=3;i<=n;i++)
    {
        d[i] = v[i] + v[i-1] + d[i-3];
        d[i]=max(d[i],d[i-1]);
        bst=max(bst,d[i]);
    }
    memset(d,0,sizeof(d));
    d[2] = v[1] + v[2];
    for(int i=4;i<n;i++){
        d[i] = v[i] + v[i-1] + d[i-3];
        d[i] = max(d[i],d[i-1]);
        bst=max(bst,d[i]);
    }
    fout<<bst;

}