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

#define MAXSTRING 51
#define MAXBASE 20

int getBit (int n, int i){
  return ((n & (1 << i)) != 0);
}

//transform string of 'y' and 'n' to a number
long long toBit(char * string){

  int size;
  int i;
  long long result=0LL;

  size=strlen(string);
  for(i=0;i<size;i++)
    if(string[i]=='y')
      result |= (1LL<<i);

  return result;
}

int main(){
  int k,K;
  int s,b;
  int i;
  char product[MAXSTRING];
  long long base[MAXBASE];
  long long poison;
  long long state;
  int nPossibilities=0;
  int conf;
  int nItems=0;
  int min,upperBound;

  FILE *in = fopen ("poisoned.in", "r");
  fscanf (in, "%d\n", &K);

  for (k = 1; k <= K; k ++){

    fscanf(in,"%d %d",&s,&b);

    for (i = 0; i < b; i++){
      fscanf(in,"%s",product);
      base[i]=toBit(product);
    }

    fscanf(in,"%s\n",product);
    poison=toBit(product);

    nPossibilities=(1<<b);
    upperBound=b+1;
    min=upperBound;

    //exhaustive search by indexing all subsets
    for (conf = 1; conf < nPossibilities; conf++){
      nItems=0;
      state=0LL;
      for (i = 0; i < b; i++){
        if(getBit(conf,i)){
          nItems++;
          state |= base[i];//add to solution
          if(
            (state&!poison>0LL)//current configuration has an element that does not belong to poison
            ||(nItems>=min)){//prune search space
            i=b;//trick to finish inner loop
          }
        }
      }

      if((nItems<min)&&(poison==state)){min=nItems;}
    }

    printf ("Data Set %d:\n", k);
    if(min<upperBound) printf ("%d\n", min);
    else printf ("Impossible.\n");
    printf ("\n");

  }

  fclose (in);
  return 0;
}