import java.util.Scanner;
import java.util.StringTokenizer;
import java.io.*;


public class problems {
    private static boolean b[] = new boolean[21];
    private static int aa[] = new int[21];
    private static int [][] a = new int[21][21];
    private static int m;
    private static int n;
    private static String ans = "";
      
    public static void main(String[] args) throws IOException {
        Scanner fi = new Scanner(new File("problems.in"));
        
        int dataSets = fi.nextInt();
        
        for (int count = 0; count < dataSets; count++) {
            for (int i = 0; i < 21; i++) {
                b[i] = false;
                aa[i] = 0;
                for (int j = 0; j < 21; j++) a[i][j] = 0;
            }
            
            ans = "";
            
            m = fi.nextInt();
            n = fi.nextInt();
            
            fi.nextLine();
            for (int i = 0; i < n; i++) {
                String s = fi.nextLine();
                StringTokenizer st = new StringTokenizer(s);
                while (st.hasMoreTokens()) {
                    int t = Integer.valueOf(st.nextToken()) - 1;
                    a[i][t] = 1;
                }
            }
            
            rec(0);
            
            System.out.println("Data Set " + (count+1) + ": " + ans);
            System.out.println();
            
        }
        
        fi.close();
    }
    
    public static void check() {
        for (int i = 0; i < m; i++) {
            if (aa[i] == 0) {
                return;
            }
        }
        String s = "";
        for (int i = 0; i < n; i++) {
            if (b[i]) s+= (char) (i+65) + " ";
        }
        
        if (s.length() < ans.length() || ans.equals("") || (s.length() == ans.length() && s.compareTo(ans) < 0)) {
            ans = s;
        }
    }
    
    public static void rec(int nn) {
        check();
        
        for (int i = nn; i < n; i++) {
            if (!b[i]) {
                b[i] = true;
                for (int j = 0; j < m; j++) aa[j] += a[i][j];
                rec(i+1);
                b[i] = false;
                for (int j = 0; j < m; j++) aa[j] -= a[i][j];
            }
        }
    }
}