#include 
#include 
#include 
#include 
using namespace std;
int main() {
    int n;
    cin >> n;
    vector v(n);
    for(int i =0 ; i < n; i++) {
        cin >> v[i];
    }
    int consecutive = 0, result = 0;
    for(int i = 0; i < n; i++) {
        if(v[i] == 1) {
            consecutive++;
        }
        else {
            result = max(result, consecutive);
            consecutive = 0;
        }
        result = max(result, consecutive);
    }
    cout << result << endl;
    return 0;
}