#include <fstream>
#include <vector>
#define MAX 100005

using namespace std;
ifstream fin ("oo.in");
ofstream fout ("oo.out");
int v[MAX];
int solve(int st, int dr) {
    if (st>dr) {
        return 0;
    }
    if (st==dr) {
        return 0;
    }
    vector<int> dp(dr+1, 0);
    for (int i=st; i<=dr; i++) {
        if (i>st) {
            dp[i]=dp[i-1];
        }
        if (i-1>=st) {
            int prec,val=v[i-1]+v[i];
            if (i-3>=st) {
                prec=dp[i-3];
            } else {
                prec=0;
            }
            dp[i]=max(dp[i], prec+val);
        }
    }
    return dp[dr];
}
int main() {
    int n,i;
    fin>>n;
    for (i=1; i<=n; i++) {
        fin>>v[i];
    }
    int ans1=v[1]+v[2]+solve(5, n-2);
    int ans2=v[2]+v[3]+solve(6, n);
    int ans3=v[n]+v[1]+solve(4, n-3);
    int ans4=solve(2, n);
    int maxim=max(max(ans1, ans2), max(ans3, ans4));
    fout<<maxim<<endl;
    return 0;
}