#include <iostream>
#include <vector>
#include <string>
#include <algorithm>

using namespace std;

int m(int n, const string &s) {
    vector<int> seg;
    int c = 0;

    for (int i = 0; i < n; ++i) {
        if (s[i] == '1') {
            c++;
            while (i < n && s[i] == '1') {
                i++;
            }
            seg.push_back(c);
            c = 0;
        }
    }

    if (seg.empty()) return 0;
    if (seg.size() == 1) return seg[0];

    return *max_element(seg.begin(), seg.end());
}

int main() {
    int t;
    cin >> t;
    while (t--) {
        int n;
        string s;
        cin >> n >> s;
        cout << m(n, s) << endl;
    }
    return 0;
}