#include <fstream>
using namespace std;
ifstream f("oo.in");
ofstream g("oo.out");
int N,Array[100005],DP[100005],Smax;
void Read()
{
    f>>N;
    int i;
    for(i=1;i<=N;i++)
        f>>Array[i];
    Array[N+1]=Array[1];
}
void Solve(int Start,int End)
{
    int i;
    DP[Start-2]=0;
    DP[Start-1]=Array[Start-2]+Array[Start-1];
    for(i=Start;i<=End;i++)
    {
        DP[i]=max(DP[i-1],DP[i-3]+Array[i-1]+Array[i]);
        Smax=max(Smax,DP[i]);
    }
}
int main()
{
    Read();
    Solve(3,N-1);
    Solve(4,N);
    Solve(5,N+1);
    g<<Smax<<"\n";
    return 0;
}