/* Genetic by Peter Schaeffer in 2000 */

#include <stdio.h>

FILE *in;
int n, l, i, j;
int b[2048][1024], d[2048];
char s[1024];

int main()
{
  in = fopen("genetic.in", "r");
  while(1)
    {
      fscanf(in, " %d %d ", &n, &l);
      if (n==0) break;
      for(i=0; i<n+n; i++)
	{
	  d[i] = 0;
	  for(j=0; j<l; j++)
	    {
	      b[i][j] = 0;
	    }
	}
      for(i=0; i<n; i++)
	{
	  fscanf(in, " %s ", s);
	  for(j=0; j<l; j++)
	    {
	      b[i+n][j] = 1 << (s[j] - 'A');
	    }
	}
      while(n>0)
	{
	  n = n/2;
	  for(i=n; i<n+n; i++)
	    {
	      d[i] = d[2*i] + d[2*i+1];
	      for(j=0; j<l; j++)
		{
		  b[i][j] = b[2*i][j] & b[2*i+1][j];
		  if (b[i][j] == 0)
		    {
		      d[i] += 1;
		      b[i][j] = b[2*i][j] | b[2*i+1][j];
		    }
		}
	      //	      printf("%3d : %d / %x - %x - %x\n", i, d[i], b[i][0], b[i][1], b[i][2]);
	    }
	}
      for(i=0; i<l; i++)
	{
	  for(j=0; j<31; j++)
	    {
	      if (b[1][i] & 1)
		{
		  printf("%c", char('A'+j));
		  break;
		}
	      b[1][i] = b[1][i] >> 1;
	    }
	}
      printf(" %d\n", d[1]);
    }
  return 0;
}