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

#define MOD 1000000007
#define ll long long
#define INF LLONG_MIN


int fukc(string &s) {
    int n = s.size();
    int mxo = 0, co = 0;
    vector<int> v;
    
    for (int i = 0; i < n; i++) {
        if (s[i] == '1') {
            co++;
        } else {
            if (co > 0) {
                v.push_back(co);
            }
            co = 0;
        }
    }
    if (co > 0) {
        v.push_back(co);
    }

    sort(v.rbegin(), v.rend());
    
    if (!v.empty()) {
        mxo = v[0];
    }
    
    return mxo;
}


void solve() {
     int t;
    cin >> t;
    while (t--) {
        int n;
        string s;
        cin >> n >> s;
        
        int ans = fukc(s);
        cout << ans << endl;
    }
    
    
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);

// #ifndef ONLINE_JUDGE
//     freopen("input.txt", "r", stdin);
//     freopen("output.txt", "w", stdout);
// #endif

    solve();
    return 0;
}