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

int main() {
    int t;
    cin >> t;
    while (t--) {
        int n;
        cin >> n;
        string s;
        cin >> s;

        int maxConsecutive = 0;
        int currentConsecutive = 0;

        for (int i = 0; i < n; i++) {
            if (s[i] == '1') {
                currentConsecutive++;
                maxConsecutive = max(maxConsecutive, currentConsecutive);
            } else {
                currentConsecutive = 0;
            }
        }

        for (int i = 0; i < n; i++) {
            if (s[i] == '0') {
                s[i] = '1';
                currentConsecutive++;
                maxConsecutive = max(maxConsecutive, currentConsecutive);
                s[i] = '0';
                currentConsecutive--;
            }
        }

        cout << maxConsecutive << endl;
    }
    return 0;
}