content: package v119;
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.PrintWriter;
  import java.util.Arrays;
  import java.util.StringTokenizer;
  
  public class SwitchTheLights_UVa11974 {
  
  	static final int INF = (int)1e9;
  	static int[][] memo;
  	static int[] lights;
  	static int M;
  	
  	static int dp(int idx, int on)
  	{
  		if(idx == M)
  			return on == 0 ? 0 : INF;
  		if(memo[idx][on] != -1)
  			return memo[idx][on];
  		return memo[idx][on] = Math.min(dp(idx + 1, on), 1 + dp(idx + 1, on ^ lights[idx]));
  	}
  	
  	public static void main(String[] args) throws Exception 
  	{
  		Scanner sc = new Scanner(System.in); 
  		PrintWriter out = new PrintWriter(System.out);
  		
  		int tc = sc.nextInt();
  		for(int t = 1; t <= tc; ++t)
  		{
  			int N = sc.nextInt();
  			M = sc.nextInt();
  			lights = new int[M];
  			for(int i = 0; i < M; ++i)
  			{
  				int x = 0;
  				for(int j = 0; j < N; ++j)
  					x |= sc.nextInt()<<j;
  				lights[i] = x;
  			}
  			memo = new int[M][1<<N];
  			for(int i = 0; i < M; ++i)
  				Arrays.fill(memo[i], -1);
  			int ans = dp(0, (1<<N) - 1);
  			if(ans == INF)
  				out.printf("Case %d: IMPOSSIBLE\n", t);
  			else
  				out.printf("Case %d: %d\n", t, ans);
  		}
  		out.flush();
  		out.close();
  	}
  
  	static class Scanner 
  	{
  		StringTokenizer st;
  		BufferedReader br;
  
  		public Scanner(InputStream s){	br = new BufferedReader(new InputStreamReader(s));}
  
  		public String next() throws IOException 
  		{
  			while (st == null || !st.hasMoreTokens()) 
  				st = new StringTokenizer(br.readLine());
  			return st.nextToken();
  		}
  
  		public int nextInt() throws IOException {return Integer.parseInt(next());}
  
  		public long nextLong() throws IOException {return Long.parseLong(next());}
  
  		public String nextLine() throws IOException {return br.readLine();}
  
  		public double nextDouble() throws IOException
  		{
  			String x = next();
  			StringBuilder sb = new StringBuilder("0");
  			double res = 0, f = 1;
  			boolean dec = false, neg = false;
  			int start = 0;
  			if(x.charAt(0) == '-')
  			{
  				neg = true;
  				start++;
  			}
  			for(int i = start; i < x.length(); i++)
  				if(x.charAt(i) == '.')
  				{
  					res = Long.parseLong(sb.toString());
  					sb = new StringBuilder("0");
  					dec = true;
  				}
  				else
  				{
  					sb.append(x.charAt(i));
  					if(dec)
  						f *= 10;
  				}
  			res += Long.parseLong(sb.toString()) / f;
  			return res * (neg?-1:1);
  		}
  
  		public boolean ready() throws IOException {return br.ready();}
  
  		public boolean nextEmpty() throws IOException
  		{
  			String s = br.readLine();
  			st = new StringTokenizer(s);
  			return s.isEmpty();
  		}
  
  
  	}
  }