/**************************************************************
    User: error408
    Language: C/C++
    School: SSDUT
    Saying: Do one thing at a time,and do well.
****************************************************************/
#include <iostream>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <algorithm>
#include <cstdio>
#include <string>
#include <cstring>
#include <cmath>
#include <ctime>
using namespace std;

#define clr(s,x) memset((s),(x),sizeof(s))
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
#define lowbit(x) (x&(-x))
#define PB push_back
#define For(i,a,b) for(int i=a;i<b;i++)
#define FOR(i,a,b) for(int i=a;i<=b;i++)
#define RL(N) scanf("%I64d",&N)
#define RLL(L,R) (RL(L),RL(R))

typedef long long               LL;
typedef unsigned int            uint;
typedef unsigned long long      ULL;
typedef vector<int>             vint;
typedef vector<string>          vstring;

/************************************END DEFINE*********************************************/

const int maxn = 1e5 + 100;
char s[maxn];
char t[maxn];
int k;

int main()
{
    int T,cas = 1;
    cin>>T;
    while(T--){
        getchar();
        gets(s);
        scanf("%d",&k);
        int len = strlen(s);
        int row = len/k;
        if(len%k)row++;
        int last = k-row*k+len;
        int cnt = 0;
        for(int i=0;i<row;i++){
            int j = i,tmp = 0;
            while(i*k+tmp+1<=len && tmp<k){
                t[cnt++] = s[j];
                if(tmp<last)j+=row;
                else j+=(row-1);
                if(last == 0)j+=1;
                tmp++;
            }
        }
        printf("Case #%d:\n",cas++);
        for(int i=0;i<cnt;i++)printf("%c",t[i]);
        puts("");
    }
    return 0;
}