LO 1023

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define test int t; cin>>t; while(t--)
ll used[100]= {0};
char ss[1000];
ll a,c,d,e=0,f;
void zxcxc(ll ind)
{

    if(ind==a)
    {
        ss[ind]='\0';
        cout<<ss<<endl;
        e++;
        return;
    }
    for(ll i=0; i<a; i++)
    {
        if(e==c) return ;
        if(used[i]==0)
        {
            used[i]=1;
            ss[ind]=(65+i);
            zxcxc(ind+1);
            used[i]=0;
        }
    }
    return;
}

int main()
{

    ll x,l;
    cin>>x;
    for(l=1; l<=x; l++)
    {
        cin>>a>>c;
        e=0;
        printf("Case %lld:\n",l);
        zxcxc(0);
        e=0;
    }
    return 0;
}