#include <iostream>
#include <vector>
#include <string>
using namespace std;
int main(int argc, char **argv)
{
    ios_base::sync_with_stdio(false);
    cin.tie(0), cout.tie(0), cout.precision(15);
    //limits?
    int T;
    cin >> T;
    cin.ignore(1);
    for(int cas = 1; cas <= T; cas ++){
        cout << "Case #" << cas << ":\n";
        //|s| 1 1e5
        string s;
        getline(cin, s);
        //1 |s|
        int K;
        cin >> K;
        cin.ignore(1);
        int n = s.size();
        int r = n%K;
        int rows = n/K;
        string t(n, ' ');
        for(int i = 0, row = 0, col = 0; i < n; i++){
            if((row == rows && col >= r) || (row == rows + 1)){
                row = 0;
                col ++;
            }
            t[row*K + col] = s[i];
            row ++;
        }
        cout << t << endl;
    }
    return 0;
}