string permutation 2

#include<bits/stdc++.h>
using namespace std;
#define op ios::sync_with_stdio(0);cin.tie(0);cout.tie(0)
int main()
{
    op;
    int t;
    cin>>t;
    for(int j=1;j<=t;j++){
        int n,k,d=0;
        cin>>n>>k;
        char c='A';
        string s;
        for(int i=1;i<=n;i++){
            s+=c;
            c++;
        }
        cout<<"Case "<<j<<":"<<"\n";
        do{
            cout<<s<<endl;
            d++;
            if(d==k) break;
        }while(next_permutation(s.begin(),s.end()));
        d=0;
    }

}