#include <bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma GCC target("sse4")
using namespace std;
bool sortbysec(const pair<int, int> &a, const pair<int, int> &b) {
  if (a.first == b.first) return (a.second < b.second);
  return (a.first > b.first);
}
void dvpii(vector<pair<int, int>> v) {
  for (int i = (0); i < (v.size()); i++) {
    cout << i + 1 << " " << v[i].first << " " << v[i].second << "\n";
  }
}
int gcd(int a, int b) {
  if (a == 0) {
    return b;
  }
  return gcd(b % a, a);
}
bool isprime(int n) {
  if (n % 2 == 0 || n % 3 == 0) return false;
  int i = 5;
  while (i * i <= n) {
    if (n % (i) == 0 || n % (i + 2) == 0) return false;
    i += 6;
  }
  return true;
}
void canonical(int n, vector<pair<int, int>> &ans) {
  for (int i = 2; i * i <= n; i++) {
    int cnt = 0;
    while (n % i == 0) {
      cnt++;
      n /= i;
    }
    if (cnt > 0) {
      ans.push_back({i, cnt});
    }
  }
}
int divisors(int a) {
  int cnt = 1;
  for (int i = 2; i <= sqrt(a); i++) {
    if (a % i == 0) {
      if (a / i == i) {
        cnt++;
      } else {
        cnt += 2;
      }
    }
  }
  return cnt;
}
void solve() {
  int n;
  cin >> n;
  string a, b;
  cin >> a >> b;
  vector<int> ans;
  for (int i = (0); i < (n); i++) {
    if (a[i] != b[i]) {
      ans.push_back(i + 1);
      ans.push_back(1);
      ans.push_back(i + 1);
    }
  }
  cout << ans.size() << " ";
  for (int X : ans) cout << X << " ";
  cout << "\n";
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int t;
  cin >> t;
  while (t--) solve();
}
