#include"cstdio"
#include"queue"
#include"cmath"
#include"stack"
#include"iostream"
#include"algorithm"
#include"cstring"
#include"queue"
#include"map"
#include"set"
#include"vector"
#define LL long long
#define mems(a,b) memset(a,b,sizeof(a))
#define ls pos<<1
#define rs pos<<1|1
using namespace std;

const int N = 1e5+5;
const int MOD = 1e9+7;
const int INF = 0x3f3f3f3f;

int n,T,k,p=1,len,id;
char ans[N];
char s[N];
int get_line(){
    int l=0;
    char c;
    while((c=getchar())!=EOF&&c!='\n') {s[l++]=c;}
    s[l]='\0';
    //cout<<s<<endl;
    return l;
}

int main(){

    scanf("%d",&T);
    while(T--){
        getchar();
        len=get_line();
        scanf("%d",&n);
        k=len/n;
        for(int i=0;i<len;i++){
            int x=i/n;
            int y=i%n;
            if(len%n){
                if(y>=len%n)
                    id=(k+1)*(len%n)+(y-len%n)*k+x;
                else id=(k+1)*y+x;
            }
            else{
                id=k*y+x;
            }
            ans[i]=s[id];
        }
        ans[len]='\0';
        printf("Case #%d:\n%s\n",p++,ans);
    }

    return 0;
}