#include <stdio.h>
#include <string.h>
#include <stdlib.h>
const int size = 2010;
int road[size][size];
int dist[size],flag[size];
char str[size][10];
#define max 999999
int distance(char str1[],char str2[])
{
	int sum=0,len,index;
	len=strlen(str1);
	for(index=0;index<len;index++)
		if(str1[index]!=str2[index])
			sum++;
		return sum;
}
int main()
{
	int n,i,j,k,sum,t;
	while(scanf("%d",&n)!=EOF&&n)
	{
		for(i=1;i<=n;i++)
		scanf("%s",str[i]);
		memset(dist,0,sizeof(dist));
		memset(road,0,sizeof(road));
		memset(flag,0,sizeof(flag));
		for(i=1;i<n;i++)
		{
			for(j=i+1;j<=n;j++)
			{
				road[i][j]=distance(str[i],str[j]);
				road[j][i]=road[i][j];
			}
		}
		sum=0;
		for(k=1;k<=n;k++)
		dist[k]=road[1][k];
		flag[1]=1;
		for(i=1;i<n;i++)
		{
			t=max;
			for(j=1;j<=n;j++)
				if(!flag[j]&&dist[j]<t)
				{
					t=dist[j];
					k=j;
				}
				sum+=t;
				flag[k]=1;
				for(j=1;j<=n;j++)
					if(!flag[j]&&road[k][j]<dist[j])
						dist[j]=road[k][j];
		}
		printf("The highest possible quality is 1/%d.\n",sum);
	}
	return 1;
}