#include <bits/stdc++.h>

#pragma GCC optimize("Ofast")
using namespace std;

void solve(int cs) {
  int n;
  cin >> n;
  string s;
  cin >> s;
  if (is_sorted(s.begin(), s.end()) || is_sorted(s.rbegin(), s.rend())) {
    cout << "0\n";
  } else {
    string t = s;
    sort(t.begin(), t.end());
    int res = 1e9;
    int cnt = 0;
    for (int i = 0; i < t.size(); i++) cnt += t[i] != s[i]; cnt = (cnt + 1) / 2;
    res = min(res, cnt);
    sort(t.rbegin(), t.rend());
    cnt = 0;
    for (int i = 0; i < t.size(); i++) cnt += t[i] != s[i]; cnt = (cnt + 1) / 2;
    cout << min(res, cnt) << "\n";
  }
}

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int tc = 1;
  cin >> tc;
  for (int cs = 1; cs <= tc; cs++) {
    solve(cs);
  }
  return 0;
}