#include <iostream>
#include <fstream>
using namespace std;
ifstream fin ("oo.in");
ofstream fout ("oo.out");
int n,v[100001];
void citire ()
{
    fin>>n;
    for(int i=1;i<=n;i++)
        fin>>v[i];
    v[n+1]=v[1];
}
int rezolvare (int a,int b)
{
    int s[100001];
    s[a+1]=v[a]+v[a+1];
    for(int i=a+2;i<=b;i++)
    {
        s[i]=max(s[i-1],s[i-3]+v[i-1]+v[i]);
    }
    return s[b];
}

int main()
{
 citire();
 fout<<max(rezolvare(1,n-1),max(rezolvare(2,n),rezolvare(3,n+1)));
}