#include<bits/stdc++.h>
using namespace std;

int main()
{
    char s[30]={'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'},c[30];
    int t,l,n,k,i,j;
    cin>>t;
    for(l=1;l<=t;l++)
    {
        cin>>n>>k;
        for(i=0;i<=n;i++)
            c[i]=s[i];
            c[n]=0;
        cout<<"Case "<<l<<":"<<endl;

        do{
            puts(c);
        }while(--k && next_permutation(c,c+n));
    }
    return 0;
}