#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define maxn 2010
struct edge{
   int a,b,value;       
}bian[maxn];
char ch[maxn][10];
int n,p[maxn];

int isbig(const void* a,const void* b)
{
    edge ta=*(edge *)a;
    edge tb=*(edge *)b;
    if (ta.value<tb.value) return -1;
    if (ta.value>tb.value) return 1;
    return 0;    
}

int find(int a)
{
    return (p[a]==0)?a:( p[a]=find(p[a]) );    
}

int compare(int a,int b)
{
    int i,t1=0;
    for (i=0;i<7;i++)
        if (ch[a][i]!=ch[b][i]) t1++;    
    return t1;
}

int main(void)
{
    freopen("1789.in","r",stdin);
    freopen("1789.out","w",stdout);
    int i,j,t,v1,v2,temp=0,count=0;
    while(1){
        temp=0;
        count=0;
        scanf("%d\n",&n);
        if (n==0) return 0;
        for (i=1;i<=n;i++) scanf("%s\n",&ch[i]);
        for (i=1;i<=n;i++)
            for (j=1;j<=n;j++){
                t=compare(i,j);
                if (t){
                    bian[++temp].a=i;
                    bian[temp].b=j;
                    bian[temp].value=t;      
                }
            }
        qsort(&bian[1],temp,sizeof(edge),isbig);
        memset(p,0,sizeof(p));
        for (i=1;i<=temp;i++){
            v1=find(bian[i].a);
            v2=find(bian[i].b);
            if (v1!=v2){
               p[v2]=v1;
               count+=bian[i].value;
            }    
        }
        printf("The highest possible quality is 1/%d.\n",count);
    }
    return 0;    
}