#include <bits/stdc++.h>
#define M 100000
using namespace std;
ifstream f("oo.in");
ofstream g("oo.out");
int n, v[M], s[M], m[M];
int main()
{
    f>>n;
    for(int i=1; i<=n; i++)f>>v[i];
    for(int i=1; i<n; i++)s[i]=v[i]+v[i+1];
    s[n]=v[1]+v[n];
    for(int i=1; i<=5; i++)s[n+i]=s[i];
    n+=5;
    //for(int i=1; i<n; i++)g<<s[i]<<" ";
    //g<<endl;
    for(int i=5; i<=n+5; i++)
    {
        m[i]=max(m[i-3]+s[i], m[i-4]+s[i]);
    }
    g<<m[n+5];
    return 0;
}