#include <bits/stdc++.h>
using namespace std;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
long long int mod = 1000000007;
const long long int N = 300001;
const long long int M = log2(N);
struct point {
  long long int x, y, i;
};
void debug(stringstream &s) {}
template <typename T, typename... Args>
void debug(stringstream &s, T a, Args... args) {
  string word;
  s >> word;
  cerr << word << " = " << a << endl;
  debug(s, args...);
}
long long int fast_exp(long long int x, long long int n) {
  if (n == 0) return 1;
  if (n & 1)
    return fast_exp(x, n - 1) * x % mod;
  else {
    long long int ans = fast_exp(x, n / 2);
    return ans * ans % mod;
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int _ = 1;
  cin >> _;
  int test = 0;
  while (_--) {
    test++;
    long long int n, m, x, y = 0, k, ans = 0;
    cin >> n;
    string a, b;
    cin >> a >> b;
    vector<long long int> sol;
    x = 0, y = n - 1;
    bool state = 0;
    for (int i = n - 1; i > 0; i--) {
      if (a[i] != b[i]) {
        if (a[0] == b[i]) {
          sol.push_back(1);
          sol.push_back(i + 1);
          for (int j = 1; j <= i; j++) {
            if (a[j] == '1')
              a[j] = '0';
            else
              a[j] = '1';
          }
          for (int j = 0; j <= i / 2; j++) {
            if (j <= i - j) swap(a[j], a[i - j]);
          }
        } else {
          sol.push_back(i + 1);
          for (int j = 0; j <= i; j++) {
            if (a[j] == '1')
              a[j] = '0';
            else
              a[j] = '1';
          }
          for (int j = 0; j <= i / 2; j++) {
            if (j <= i - j) swap(a[j], a[i - j]);
          }
        }
        state = state ^ 1;
      }
    }
    if (a[0] != b[0]) sol.push_back(1);
    cout << sol.size() << "\n";
    for (auto i : sol) cout << i << " ";
    cout << "\n";
  }
  return 0;
}
