#include <stdio.h>
#include <stdlib.h>


struct edge {
	short from, to, q;
} edges[2000 * 1000 + 10];
int nedges;

char data[10000][10];
int sums[10000];
char line[100];
int n;

int rank[10000];
int parent [10000];


void init () {
	int i;
	for (i = 0; i < n; i++) {
		rank[i] = 0;
		parent[i] = i;
	}
}

int find(int v) {
	int x = v;

	while (x != parent[x]) {
		x = parent[x];
	}
	while (v != parent[v]) {
		int vv = parent[v];
		parent[v] = x;
		v = vv;
	}
	return x;
}

void un (int a, int b) {
	a = find(a);
	b = find(b);
	if (rank[a] < rank[b]) {
		parent[a] = b;
	} else if (rank[a] > rank[b]) {
		parent[b] = a;
	} else {
		parent[a] =b;
		rank[b] ++;
	}
}


int cmp (struct edge *a, struct edge*b) {
	return a->q - b->q;
}


int main() {
	int i,j,k,s;
	int m;
	while(1) {
		gets(line);
		sscanf(line,"%d",&n);
		if (!n)
			break;

		i = n;
		nedges = 0;
		while (i--) {
			gets(data[i]);
			sums[i] = 0;
		}

		for(i = 0; i < n; i++) {
			for (j = i+1; j < n; j++) {
				s = 0;
				for (k = 0; k < 7; k++) {
					if (data[i][k] != data[j][k]) 
						s++;
				}
				edges[nedges].from = i;
				edges[nedges].to = j;
				edges[nedges++].q = s;
				edges[nedges].from = j;
				edges[nedges].to = i;
				edges[nedges++].q = s;
			}
		}

		qsort(edges,nedges,sizeof(struct edge),cmp);

		m = 0;
		init();
		
		for (i = 0; i < nedges; i++ ) {
			int a = find(edges[i].from);
			int b = find(edges[i].to);
			if (a != b) {
				un (a, b);
				m += edges[i].q;
			}
		}

		printf("The highest possible quality is 1/%d.\n",m);
	}
	return 0;
}