#include <stdio.h>
#include <string.h>

char bit (int n, int b)
{
  n = n / (1 << b);
  n = n%2;
  return (n > 0);
}

int main (void)
{
  int K, k, M, m, N, n;
  int T, t, B, b;
  int c[21];
  char s[1001];

  FILE *in = fopen ("problems.in", "r");

  fscanf (in, "%d\n", &K);

  for (k = 1; k <= K; k ++)
    {
      printf ("Data Set %d: ", k);
      fscanf (in, "%d %d\n", &M, &N);
      for (n = 0; n < N; n ++)
	{
	  int i;
	  char *ts;

	  c[n] = 0;
	  fgets (s, 1001, in);
	  s[strlen(s)-1] = 0;
	  for (i = 0, ts = strtok(s, " \n"); ts != NULL; 
	       i ++, ts = strtok(NULL, " \n"))
	    {
	      sscanf (ts, "%d", &m); m --;
	      c[n] = c[n] | (1 << m);
	    }      
	}
      T = 0; B = M+1;
      for (t = 0; t < (1 << N); t ++)
	{
	  int cc = 0;
	  b = 0;
	  for (n = 0; n < N; n ++)
	    if (bit(t, N-1-n)) { b ++; cc = cc | c[n]; }
	  if (cc == (1 << M) -1 && b <= B) { T = t; B = b; }
	}
      b = 1;
      for (n = 0; n < N; n ++)
	if (bit(T, N-1-n)) 
	  { 
	    printf ("%c", 'A' + n);
	    if (b < B) printf (" ");
	    b ++;
	  }
      if (k < K) printf ("\n");	      
    }

  fclose (in);
  return 0;
}