#include <fstream>
#define DIM 100005
using namespace std;
ifstream fin("oo.in");
ofstream fout("oo.out");
int n,i,v[DIM],d[DIM];

int din(int st,int dr) {
    d[st]=0;
    d[st+1]=v[st]+v[st+1];
    for (int i=st+2;i<=dr;i++)
        d[i]=max(d[i-1],d[i-3]+v[i-1]+v[i]);
    return d[dr];
}

int main() {
    fin>>n;
    for (i=1;i<=n;i++)
        fin>>v[i];
    v[n+1]=v[1];
    fout<<max(din(1,n-1),max(din(2,n),din(3,n+1)));
    return 0;
}