#include<stdio.h>
#include<algorithm>
usingnamespacestd;inte[2200][2200];chars[2200][7];intmain(){intdis[2200];boolflag[2200];intN,inf=999999;while(scanf("%d",&N),N){for(inti=1;i<=N;i++){dis[i]=inf;flag[i]=false;}for(inti=1;i<=N;i++){for(intj=1;j<=N;j++){e[i][j]=inf;}}for(inti=1;i<=N;i++)scanf("%s",s[i]);for(inti=1;i<=N;i++){for(intj=1;j<=N;j++){if(i==j)continue;intcnt=0;for(intk=0;k<7;k++){if(s[j][k]!=s[i][k])cnt++;}e[i][j]=e[j][i]=cnt;}}intsum=0;dis[1]=0;while(true){intv=-1;for(intu=1;u<=N;u++){if(!flag[u]&&(v==-1||dis[u]<dis[v]))v=u;}if(v==-1)break;flag[v]=true;sum+=dis[v];for(intu=1;u<=N;u++){dis[u]=min(dis[u],e[v][u]);}}printf("The highest possible quality is 1/%d.\n",sum);}return0;}