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

int main(){
    int T;
    cin >> T;
    while(T--) {
        int N;
        string S;
        cin >> N >> S;
        int one = count(S.begin(), S.end(), '1');
        int zero = N-one;
        cout << max(one,zero) << endl;
        }
}