#include <bits/stdc++.h>

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

int n, mx, v[100005];
int dp[100005], dp2[100005], dp3[100005];

int main() {
    fin >> n;
    
    for (int i=0;i<n;i++) {
        fin >> v[i];
    }
    
    for (int i=1;i<n;i++) {
        int c1 = dp[(i+n-3)%n] + v[(i+n-1)%n] + v[i];
        int c2 = dp[(i+n-4)%n] + v[(i+n-1)%n] + v[i];
        int c3 = dp[(i+n-5)%n] + v[(i+n-1)%n] + v[i];
        
        if (i >= 1 && i < n-3) dp[i] = max(max(c1, c2), c3);
        if (i >= 2 && i < n-2) dp2[i] = max(max(c1, c2), c3);
        if (i >= 3 && i < n-1) dp3[i] = max(max(c1, c2), c3);
        
        //cout << max(max(dp[i], dp2[i]), dp3[i]) << " ";
        mx = max(mx, max(max(dp[i], dp2[i]), dp3[i]));
    }
    
    fout << mx;
    return 0;
}