#include <stdio.h>
#define MAX_N 2001

char trucks[MAX_N][7];

int vzdalenost(int co,int koho) {
  int ret=0;

  ret+=trucks[co][0]!=trucks[koho][0];
  ret+=trucks[co][1]!=trucks[koho][1];
  ret+=trucks[co][2]!=trucks[koho][2];
  ret+=trucks[co][3]!=trucks[koho][3];
  ret+=trucks[co][4]!=trucks[koho][4];
  ret+=trucks[co][5]!=trucks[koho][5];
  ret+=trucks[co][6]!=trucks[koho][6];

  return ret;
}

int main(void) {
  int i,j,N;
  int sum;
  int docas[MAX_N];
  int vzdal[MAX_N];
 
  while (scanf("%d",&N),N) {
    sum=0;

    for (i=0;i<N;i++) {
      scanf("%s",trucks[i]);
      docas[i]=1;
      vzdal[i]=10;
    }

    vzdal[0]=0;
    for (j=0;j<N;j++) {
      int s,min,mini=-1;
      
      for (i=0;i<N;i++) if (docas[i]) {
	if (mini==-1) {mini=i;min=vzdal[i];}
	else if (vzdal[i] < min) {mini=i;min=vzdal[i];}
      }

      docas[mini]=0;
      for (s=0;s<N;s++) if (docas[s]) {
	int local=vzdalenost(mini,s);

	if (local < vzdal[s])
	  vzdal[s]=local;
      }
      sum+=vzdal[mini];	
    }
    
    printf("The highest possible quality is 1/%d.\n",sum);
  }

  return 0;
}