#include <bits/stdc++.h>
using namespace std;
ifstream fin("oo.in");
ofstream fout("oo.out");

int v[1000005], dp[1000005];
int n, add, rez;

int solve(int st, int fn) {
    for (int i = 1; i <= n + 1; i++)
        dp[i] = 0;
        
    for (int i = st + 1; i <= st + fn - 1; i++) {
        add = 0;
        
        if (i >= 4) {
            add = dp[i - 3];
        }
        
        dp[i] = max(dp[i - 1], v[i - 1] + v[i] + add);
    }
    
    return dp[st + n - 2];
}

int main() {
    fin >> n;
    for (int i = 1; i <= n; i++)
        fin >> v[i];
        
    v[n + 1] = v[1];
    
    rez = max(solve(3, n), solve(1, n));
    rez = max(rez, solve(2, n));
    
    fout << rez;

    return 0;
}