#include <bits/stdc++.h>   using namespace std;   long long int a[2005];   long long int cnt[2005];   long long int b[2005];   long long int vis[2005];   vector<long long int> v;   vector<long long int> vv;   vector<long long int> ans;   long long int prime[2005];   bool pr[2005];   set<char> st;   priority_queue<long long int> bob;   priority_queue<long long int> ali;   priority_queue<long long int> bth;   queue<long long int> q;   map<long long int, long long int> mp;   long long int taken[105];   map<long long int, long long int>::iterator it;   map<long long int, vector<long long int> > ck;   string ss, tt;   long long int pos[205];   long long int afs[205];   long long int pre[2005];   long long int aa[2005];   long long int cs[27];   long long int ct[27];   long long int power(long long int k, long long int i) {     long long int res = 1;     for (long long int j = 1; j <= i; j++) {       res = res * k;     }     return res;   }   int main() {     long long int n, i, j, k, t, m;     cin >> t;     long long int minis;     long long int res;     long long int x, y;     long long int pp;     string fg;     long long int l, r;     long long int h;     long long int p, q;     string tt;     while (t--) {       v.clear();       cin >> n;       cin >> ss >> tt;       string fg;       long long int kk = n;       res = 0;       for (i = n - 1; i >= 0; i--) {         if (ss[i] == tt[i]) {           kk--;           continue;         } else {           if (ss[0] == tt[i]) {             res = res + 1;             v.push_back(1);             if (ss[0] ==  0 )               ss[0] =  1 ;             else               ss[0] =  0 ;           }           fg.clear();           for (j = 0; j <= i; j++) {             if (ss[j] ==  0 )               fg.push_back( 1 );             else               fg.push_back( 0 );           }           reverse(fg.begin(), fg.end());           res = res + 1;           v.push_back(kk);           for (j = 0; j <= i; j++) {             ss[j] = fg[j];           }         }         kk--;       }       cout << res <<    ;       for (i = 0; i < v.size(); i++) cout << v[i] <<    ;       cout <<   n ;     }     return 0;   }   