#include <iostream>
#include<vector>
using namespace std;
int main()
{
    vector<int> v;
    int sum = 0,n;
    cin >> n;
    for (int i = 0; i < n; i++) {
        int k;
        cin >> k;
        v.push_back(k);
    }
    for (int i = 0; i < v.size(); i++) {
        int temp = v[i];
        for (int j = i + 2; j < v.size(); j+=2) {
            temp += v[j];
        }
        sum = max(sum, temp);
    }
    cout << sum;
}