#include <fstream>
#define DIM 100001
using namespace std;
int n,v[DIM],d[DIM],i,d2[DIM],d3[DIM],x;
ifstream fin ("oo.in");
ofstream fout ("oo.out");

int main (){

    fin>>n;
    for (i=1;i<=n;i++)
        fin>>v[i];
    d[1] = v[1]+v[n];
    for (i=3;i<n-1;i++){
        d[i] = max (d[i-1],v[i]+v[i-1]+d[i-3]);
    }

    for (i=1;i<n;i++){
        d2[i] = max (d2[i-1],v[i]+v[i-1]+d2[i-3]);
    }
    for (i=3;i<=n;i++)
        d3[i] = max (d3[i-1],v[i]+v[i-1]+d3[i-3]);

    x = max (d[n-2],d2[n-1]);
    x = max (x,d3[n]);
    fout<<x;
    /*if (d2[n-1] > d[n-2])
        fout<<d2[n-1];
    else
        fout<<d[n-2];
        */
    return 0;
}