#include<bits/stdc++.h>
using namespace std;
int flag=0;
struct node
{
    bool endmark;
    node *next[10];
    node()
    {
        endmark=false;
        for(int i=0; i<10; i++)
            next[i]=NULL;
    }
}*root;

void insert(char *str,int len)
{
    node *curr=root;
    for(int i=0; i<len; i++)
    {
        int id=str[i]-'0';
        if(curr->next[id]==NULL)
            curr->next[id]=new node();
        curr=curr->next[id];
        if(curr->endmark==1)
            flag=1;
    }
    curr->endmark=1;
}


void del(node *cur)
{
    for(int i=0; i<10; i++) if(cur->next[i])
            del(cur->next[i]) ;
    delete(cur) ;
}


int main()
{

    root=new node();
    int num_word,j=1,T;

    cin>>T;

    while(T--)
    {
        flag=0;
        cin>>num_word;

        for(int i=1; i<=num_word; i++)
        {

            char str[50];
            scanf("%s",str);
            insert(str,strlen(str));
        }
        if(flag==1)
            cout<<"Case "<<j<<": NO"<<endl;
        else
            cout<<"Case "<<j<<": YES"<<endl;
        j++;
        del(root);

    }
    return 0;
}