#include <cstdio>
#include <cstring>
#include <map>
#include <cmath>
#include <queue>
#include <string>
#include <stack>
#include <cstdlib>
#include <iostream>
#include <algorithm>
#define abs(x) ((x)>0?(x):-(x))
#define __max(a,b) ((a)>(b)?(a):(b))
#define __min(a,b) ((a)<(b)?(a):(b))
#define rep(i,repstt,repend) for(int i=repstt;i<repend;i++)
#define erep(i,repstt,repend) for(int i=repstt;i<=repend;i++)
#define inf 0x7f//2147483647
#define iinf 0xffffff
#define PI acos(-1.0)
#define NOBUG puts("No_Bug_Hear");
#define STOP system("pause");
#define FOUT freopen("out.txt","w",stdout);
#define FIN freopen("in.txt","r",stdin);
#define OUTCLOSE fclose(stdout);
#define INCLOSE fclose(stdin);
#define INIT(a,b) memset(a,b,sizeof(a))
typedef long long ll;
using namespace std;
char f[2020][8];
int dis[2020],n;
bool vst[2020];
int __d(char *ca,char *cb){
	int cnt=0;
	rep(i,0,7)
		if(ca[i]!=cb[i])
			cnt++;
	return cnt;
}
int prim(){
	int tot=0;
	INIT(vst,0);
	rep(i,0,n)dis[i]=iinf;
	dis[0]=0;
	rep(i,0,n){
		int tmin=iinf,k;
		rep(j,0,n)
			if(!vst[j]&&dis[j]<tmin){
				tmin=dis[j];
				k=j;
			}
		vst[k]=1;
		//if(tmin==iinf)	return -1;
		tot+=tmin;
		rep(j,0,n)
		if(!vst[j])
			dis[j]=__min(dis[j],__d(f[k],f[j]));
	}
	return tot;
}
int main(){
	//FIN
	//FOUT
	while(scanf("%d",&n)&&n){
		getchar();
		rep(i,0,n)gets(f[i]);
		printf("The highest possible quality is 1/%d.\n",prim());
	}
	//INCLOSE
	//OUTCLOSE
	return 0;
}