#include<iostream>

 #include<cstdio>

 #include<cstring>

 #include<algorithm>

 using namespace std;

 bool map[][];

 int mark[];

 char str[];

 int n,ans;

 bool Judge(int x,int color)

 {

     for(int i=;i<n;i++){

         if(i!=x&&map[x][i]&&mark[i]==color)

             return ;

     }

     return ;

 }

 void dfs(int pos)

 {

     if(pos==n){

         ans=min(ans,*max_element(mark,mark+n));

         return ;

     }

     for(int i=pos;i<n;i++){

         for(int j=;j<=;j++){

             if(Judge(i,j)){

                 mark[i]=j;

                 dfs(i+);

             }

         }

     }

 }

 int main()

 {

     while(~scanf("%d",&n)&&n){

         memset(map,false,sizeof(map));

         for(int i=;i<n;i++){

             scanf("%s",str);

             for(int j=;j<strlen(str);j++){

                 map[i][str[j]-'A']=true;

                 map[str[j]-'A'][i]=true;

             }

         }

         memset(mark,,sizeof(mark));

         ans=;

         mark[]=;

         dfs();

         if(ans==){

             printf("1 channel needed.\n");

         }else

             printf("%d channels needed.\n",ans);

     }

     return ;

 }