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

int main() {
    int T;
    cin >> T;
    
    while (T--) {
        int N;
        string S;
        cin >> N >> S;
        
        // Count the number of consecutive '1's blocks
        vector<int> onesBlocks;
        int count = 0;

        for (int i = 0; i < N; ++i) {
            if (S[i] == '1') {
                count++;
            } else {
                if (count > 0) {
                    onesBlocks.push_back(count);
                }
                count = 0;
            }
        }

        if (count > 0) {
            onesBlocks.push_back(count); // If the string ends with 1's
        }

        // If no blocks of 1's are found, answer is 0
        if (onesBlocks.empty()) {
            cout << 0 << endl;
        } else {
            // The longest block of consecutive 1's will be the result
            int maxConsecutiveOnes = *max_element(onesBlocks.begin(), onesBlocks.end());
            cout << maxConsecutiveOnes << endl;
        }
    }
    return 0;
}