#include <bits/stdc++.h>

using namespace std;

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

int n;
int v[100001], dp[100001];

int main() {
    in >> n;
    for (int i = 1; i <= n; ++i)
        in >> v[i];
    dp[1] = v[1] + v[n];
    int rez = dp[1];
    for (int i = 2; i < n; ++i) {
        dp[i] = v[i - 1] + v[i];
        int it = 1;
        if (i == n - 1)
            ++it;
        for (int j = it; j <= i - 3; ++j) {
            dp[i] = max(dp[i], dp[j] + v[i - 1] + v[i]);
            rez = max(rez, dp[i]);
        }
    }
    return out << rez, 0;
}