#include <stdio.h>
#include <string.h>

int main()
{
	int n,i,j,l,p,m;
	char s[2100][15];
	char v[2000][2000];
	while (1)
	{
		scanf("%d",&n);
		if (n==0) break;
		gets(s[0]);
		for (i=0;i<n;i++) 
		{
			gets(s[i]);
		}
		m=strlen(s[0]);
		for (i=0;i<n;i++) for (j=0;j<n;j++) 
		{
			p=0;
			for (l=0;l<m;l++) if (s[i][l]!=s[j][l]) p++;
			v[i][j]=p;
			v[j][i]=p;
		}
		p=1000000000;
		for (i=0;i<n;i++) 
		{
			l=0;
			for (j=0;j<n;j++) l+=v[i][j];
			if (l<p) p=l;
		}
		printf("The highest possible quality is 1/%d.\n",p);
	}
	return 0;
}