1 #include<cstdio>
2 #include<cstring>
3 using namespace std;
4 int n;
5 int a[30][30];
6 int c[30];
7
8 bool pd(int x,int color)
9 {
10 for (int i=1;i<x;i++)
11 if (a[x][i]==1 && c[i]==color) return false;
12 return true;
13 }
14
15 bool dfs(int x,int color)
16 {
17 if (x>n) return true;
18 for (int i=1;i<=color;i++)
19 if (pd(x,i))
20 {
21 c[x]=i;
22 return dfs(x+1,color);
23 }
24 return false;
25 }
26 int main()
27 {
28 scanf("%d",&n);
29 while (n!=0)
30 {
31 memset(a,0,sizeof(a));
32 for (int i=1;i<=n;i++)
33 {
34 char str[30];
35 scanf("%s",str);
36 for (int j=2;j<strlen(str);j++)
37 {
38 a[str[0]-'A'+1][str[j]-'A'+1]=1;
39 a[str[j]-'A'+1][str[0]-'A'+1]=1;
40 }
41 }
42 if (dfs(1,1)) printf("1 channel needed.\n");
43 else
44 {
45 for (int i=2;i<=4;i++)
46 if (dfs(1,i))
47 {
48 printf("%d channels needed.\n",i);
49 break;
50 }
51 }
52 scanf("%d",&n);
53 }
54 return 0;
55 }
