#include<stdio.h>
#include<string>
#include<iostream>
using namespace std;
char s1[1000001];
int main()
{
    int t;
    int i, j, k, x, y;
    int n;
    //string s;
    char s[1000001];
    cin >> t;
    getchar();
    for(i=1; i<=t; i++)
    {
        //scanf("%s", s);
        //gets(s);
        j = 0;
        while((s[j] = getchar()) != '\n')
        {
            j++;
        }
        n = j;
        s[n] = '\0';
        //getline(cin, s);
        cin >> k;
        getchar();
        //cout << s.size() << endl;
        cout << "Case #" << i << ":\n";
        y = 0;
        for(j=0; j<k; j++)
        {
            for(x=j; x<n; x+=k)
            {
                s1[x] = s[y++];
            } 
        }
        for(j=0; j<n; j++)
        {
            cout << s1[j];
        }
        cout << endl;
    }
}