#include <vector> 
#include <list> 
#include <map> 
#include <set> 
#include <deque> 
#include <queue> 
#include <stack> 
#include <bitset> 
#include <algorithm> 
#include <functional> 
#include <numeric> 
#include <utility> 
#include <sstream> 
#include <iostream> 
#include <iomanip> 
#include <cstdio> 
#include <cmath> 
#include <cstdlib> 
#include <cctype> 
#include <string> 
#include <cstring> 
#include <ctime> 

using namespace std;

#define _int64 long long

char s[110000];

int main()
{
  int i,j,l,t,n,x,y,lastx,lasty,lim,mm,m;
  string ss;
  scanf("%d",&t);
  gets(s);
  for (l=0;l<t;l++)
  {
    gets(s);
    ss=s;
    n=ss.length();
    scanf("%d",&m);
    gets(s);
    printf("Case #%d:\n",l+1);
    lastx=(n-1)/m;lasty=(n-1)%m;
    mm=lastx+1;
    //cout<<lastx<<" "<<lasty<<endl;
    lim=(lasty+1)*(lastx+1);
    for (i=0;i<n;i++)
    {
      if (i<lim)
      {
        y=i/mm;
        x=i%mm;
      }
      else
      {
        y=(i-lim)/(mm-1)+lasty+1;
        x=(i-lim)%(mm-1);
      }
      s[x*m+y]=ss[i];
    }
    s[n]=0;
    printf("%s\n",s);
  }
  return 0;
}