/**
 * This class can take a variable number of parameters on the command
 * line. Program execution begins with the main() method. The class
 * constructor is not invoked unless an object of type 'Class1'
 * created in the main() method.
 */
import java.io.*;
import java.util.StringTokenizer;



public class proba
{
		static boolean [][] problem;
		static int [] num;
		int [] cat;
	/**
	 * The main entry point for the application. 
	 *
	 * @param args Array of parameters passed to the application
	 * via the command line.
	 */
	public static void main (String[] args)throws IOException
	{
		BufferedReader in=new BufferedReader(new FileReader("proba.in"));
		PrintWriter out=new PrintWriter(new FileWriter("proba.out"));
		StringTokenizer token;
		int n=Integer.parseInt(in.readLine());
		int M,N;
		for (int i=0;i<n;i++){
			token=new StringTokenizer(in.readLine());
			M=Integer.parseInt(token.nextToken());
			N=Integer.parseInt(token.nextToken());
			//System.out.println("M"+M+" N"+N);
			problem=new boolean [N][M];
			num=new int[N];
			for(int j=0;j<N;j++){
				token=new StringTokenizer(in.readLine());
				while(token.hasMoreTokens()){
					int prob=Integer.parseInt(token.nextToken());
					num[j]++;
					problem[j][prob-1]=true;
				}
			}
			//System.out.println("Data read");
			boolean done=false;
			int path[]=new int[N];
			int s=0;
			for(int depth=1;depth<N+1 && !done;depth++){//iterative deepening
				//System.out.println("depth="+depth);
				//s=0
				//for(int start=0;start<N && !done;start++){
					//System.out.println("Starting on "+start);
					boolean [][] state=new boolean[N+1][M];
					s=0;
					boolean used[][]=new boolean[N+1][N];
					path=new int[N+1];
					//path[s]=start;
					//used[s][0]=true;
					//state[s]=or(state[0],problem[start]);
					do{
						//System.out.println("State="+state[s]);
						if(s>=depth){
							s--;
							
						}else{
							//find next
							int x;
							for( x=0;x<N;x++){
								if(!used[s][x]){
									//System.out.println("Spot "+x);
									used[s][x]=true;
									s++;
									//System.out.println("s="+s);
									//if(s>=depth)break;
									state[s]=or(state[s-1],problem[x]);
									used[s]=or(used[s-1],new boolean[N]);
									path[s]=x;
									break;
								}
							}
							if(x>=N){
								s--;
								continue;
							}
							//System.out.println("next state");
							//if (s>=depth)continue;
							if( ended(state[s])){
								done=true;
								break;
							}
						}
									
			
					}while(s>=0);


				//}

			}
			//output for data set
			out.print("Data Set "+(i+1)+":");
			for (int l=1;l<=s;l++) out.print(" "+ (char)('A'+path[l]));
			out.println();
			out.println();
		}


		out.flush();
		out.close();
	}

	static boolean[] or(boolean[]a, boolean[]b){
		int x=a.length;
		boolean ans[]=new boolean[x];
		for(int y=0;y<x;y++){
			ans[y]=a[y] || b[y];
		}
		return ans;
	}
	static boolean ended(boolean[] a){
		int n=a.length;
		for(int x=0;x<n;x++){
			if(!a[x])return false;
		}
		return true;
	}
}