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

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int tt;
  cin >> tt;
  while (tt--) {
    int n; 
    string s; 
    cin >> n >> s; 
    int one = count(s.begin(), s.end(), '1');
    cout << one - max(count(s.begin(), s.begin() + one, '1'), count(s.rbegin(), s.rbegin() + one, '1')) << '\n';
  }
  return 0;
}