1. // #include <format>
  2. #include <climits>
  3. #include <iostream>
  4. #include <fstream>
  5. #include <assert.h>
  6. #include <algorithm>
  7. #include <vector>
  8. #include <set>
  9. #include <string>
  10. #include <queue>
  11. #include <map>
  12.  
  13. # define pb push_back 
  14. #define pii pair<int, int>
  15. #define mp make_pair
  16. # define ll long long int
  17.  
  18. using namespace std;
  19.   
  20. FILE *fp;
  21. ofstream outfile;
  22.  
  23. const int maxt = 100, maxsumn = 1000;
  24. char seq[4] = {'A', 'T', 'C', 'G'};
  25. int main()
  26. {   
  27.     
  28.     int t; cin >> t;
  29.     int sumn = 0;
  30.     while(t--){
  31.         int n; cin >> n;
  32.         assert(n % 2 == 0);
  33.         sumn += n;
  34.         string s; cin >> s;
  35.         for(char c : s)assert(c == '0' || c == '1');
  36.         for(int i = 0; i < n; i += 2){
  37.             cout << seq[(s[i] - '0') * 2 + (s[i + 1] - '0')];
  38.         }
  39.         cout << endl;
  40.     }
  41.     assert(sumn <= maxsumn);
  42.     // assert(getchar()==-1);
  43. }