#include <bits/stdc++.h>

using namespace std;
ifstream fin("oo.in");
ofstream fout("oo.out");

int n, v[100005];
int dp[100005];

int main() {
    fin >> n;
    
    for (int i=0;i<n;i++) {
        fin >> v[i];
    }
    
    for (int i=2;i<n;i++) {
        dp[i] = max(dp[(i+n-4)%n] + v[(i+n-1)%n] + v[i], dp[(i+n-3)%n] + v[(i+n-1)%n] + v[i]);
        //cout << dp[i] << " ";
    }
    
    fout << dp[n-1];
    return 0;
}