// No.45 回転寿司
// https://yukicoder.me/problems/no/45
//

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int solve(vector<int> &osushi);


int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    unsigned int N;
    cin >> N;
    vector<int> osushi(N);
    for (auto i = 0; i < N; ++i)
        cin >> osushi[i];
    int ans = solve(osushi);
    cout << ans << endl;
}

int solve(vector<int> &osushi) {
    int next_OK = 0;
    int next_NG = osushi[0];

    for (auto i = 1; i < osushi.size(); ++i) {
        int temp = next_NG;
        next_NG = next_OK + osushi[i];
        next_OK = max(next_OK, temp);
    }
    return max(next_OK, next_NG);
}