#include <bits/stdc++.h>
using namespace std;

int main()
{
    int n;
    cin >> n;
    vector<int> v(n);
    for (int i = 0; i < n; i++) cin >> v.at(i);
    int taken = v.at(0), nottaken = 0;
    for (int i = 1; i < n; i++) {
        int taken_new = nottaken + v.at(i);
        nottaken = max(taken, nottaken);
        taken = taken_new;
    }
    cout << max(taken, nottaken) << endl;
}