#include<cstdio>
#define N 100005
using namespace std;
int n,k,row,rest,x,y,i,T,Test;char ch,a[N],ans[N];
int main()
{
    scanf("%d",&Test);
    while (Test--)
    {
        getchar();
        for (n=0,ch=getchar();ch!='\n'&&ch!='\r';a[++n]=ch,ch=getchar());
        scanf("%d",&k);
        if (k>n) k=n;
        row=n/k+(n%k>0);
        rest=n-(row-1)*k;
        x=0;y=1;
        for (i=1;i<=n;i++) 
        {
            x++;
            if (x==row&&y>rest||x>row) x=1,y++;
            ans[(x-1)*k+y]=a[i];
      }
      printf("Case #%d:\n",++T);
      for (i=1;i<=n;i++)
          printf("%c",ans[i]);
      puts("");
  }
}