#include <bits/stdc++.h>

using namespace std;

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

const int NMAX = 1e5;
int a[NMAX+5], dp[NMAX+5], n;

int solve(const int &start) {
    for (int i = 1; i <= n+1; i++)
        dp[i] = 0;
    for (int i = start+1; i < start+n-1; i++)
        dp[i] = max(dp[i-1], dp[max(i-3, 0)]+a[i-1]+a[i]);
    return dp[start+n-2];
}

int main() {
    ios_base :: sync_with_stdio(false);
    fin.tie(nullptr), fout.tie(nullptr);
    
    fin>>n;
    for (int i = 1; i <= n; i++)
        fin>>a[i];
    a[n+1] = a[1];
    fout<<max({solve(1), solve(2), solve(3)});
    return 0;
}