#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

vector<int> max_sum;

void calc_max(vector<int> v,int sum,int key,int num) {
	sum += v[key];
	if (key == num - 2 || key == num - 1) {
		max_sum.push_back(sum);
	}
	else {
		for (; key + 2 < num; key++) {
			calc_max(v, sum, key + 2, num);
		}
	}
}

int main() {
	int num;
	cin >> num;
	vector<int> v;
	for (int i = 0; i < num; i++) {
		int temp; cin >> temp;
		v.push_back(temp);
	}
	for (int i = 0; i < num; i++) {
		calc_max(v, 0 ,i,num);
	}
	sort(max_sum.begin(), max_sum.end());
	cout << max_sum[max_sum.size() - 1] << endl;
}