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

int main() {
  int t;
  cin >> t;
  while (t--) {
    int n; cin >> n;
    string s; cin >> s;
    int cnt0 = 0, cnt1 = 0;
    for (int i = 0; i < n; i++) {
      cnt0 += s[i] == '0';
      cnt1 += s[i] == '1';
    }
    int ans = 2 * min(cnt0, cnt1) + (cnt0 != cnt1);
    cout << ans << '\n';
  }
  return 0;
}