1 import java.util.*; 2 import java.math.*; 3 public class Main { 4     public static boolean flag=false; 5     public static int ans=0; 6     public static void main(String []args) 7     { 8         Scanner cin=new Scanner(System.in); 9         int n;10         String str;11         while(cin.hasNext())12         {13             ans=1;14             int [][]g=new int[100][100];15             int []hash=new int[100];16              n=cin.nextInt();17              if(n==0) break;18              for(int i=0; i<n; i++)19              {20                  str=cin.next();21                  for(int j=2; j<(int)str.length(); j++)22                  {23                      g[str.charAt(0)-‘A‘][str.charAt(j)-‘A‘]=1;24                  }25              }26              flag=false;27              dfs(0,1,g,n,hash);28              if(ans==1)29              {30              System.out.println("1 channel needed.");31              }32              else33              {34                  System.out.println(ans+" channels needed.");35              }36         }37     }38     public static int deal(int id,int co,int n,int g[][],int hash[])39     {40         for(int i=0; i<n; i++)41         {42             if(g[id][i]==1&&co==hash[i])43             {44                 return 0;45             }46         }47         return 1;48     }49     public static void dfs(int num,int m1,int g[][],int n,int hash[])50     {51         if(flag) return;52         if(num>=n)53         {54             flag=true;55             return;56         }57         for(int i=1; i<=m1; i++)58         {59             if(deal(num,i,n,g,hash)==1)60             {61                 hash[num]=i;62                 dfs(num+1,m1,g,n,hash);63                 hash[num]=0;64             }65         }66         if(flag==false)67         {68             ans++;69             dfs(num,m1+1,g,n,hash);70         }71     }72 }