#include <bits/stdc++.h>

using namespace std;

ifstream f("oo.in");
ofstream g("oo.out");

int n, v[100001], dp[100001];

void citire()
{
    f >> n;
    for(int i = 1;i <= n;i ++)
        f >> v[i];
}

void suma(){
    for(int i = 1;i < n;i ++)
        v[i] = v[i] + v[i + 1];
    v[n] = v[n] + v[1];
}

void dinamic()
{
    for(int i = 1;i < n - 1;i ++)
        dp[i] = max(dp[i - 1], v[i] + dp[i - 3]);

    g << *max_element(dp + 1, dp + 1 + n);
}

int main()
{
    citire();
    suma();
    dinamic();
    return 0;
}