#include <iostream>#include <cstdio>#include <cstdlib>#include <cstring>using namespace std;#define maxn 2005#define inf 0x3f3f3f3fint n;char pre[maxn][10];int cost[maxn][maxn];int vis[maxn];int lowc[maxn];int cal(int a, int b){ int ret = 0; for (int i = 0; i < 7; i++) if (pre[a][i] != pre[b][i]) ret++; return ret;}int prim(){ int i, j, p; int minc, res = 0; memset(vis, 0, sizeof(vis)); vis[0] = 1; for (i = 1; i < n; i++) lowc[i] = cost[0][i]; for (i = 1; i < n; i++) { minc = inf; p = -1; for (j = 0; j < n; j++) if (0 == vis[j] && minc > lowc[j]) { minc = lowc[j]; p = j; } if (inf == minc) return -1; res += minc; vis[p] = 1; for (j = 0; j < n; j++) if (0 == vis[j] && lowc[j] > cost[p][j]) lowc[j] = cost[p][j]; } return res;}int main(){ while (scanf("%d", &n), n) { memset(cost, 0, sizeof(cost)); getchar(); for (int i = 0; i < n; i++) gets(pre[i]); for (int i = 0; i < n - 1; i++) for (int j = i + 1; j < n; j++) { cost[i][j] = cal(i, j); cost[j][i] = cost[i][j]; } printf("The highest possible quality is 1/%d.n", prim()); } return 0;}
