#include <iostream>
#include <cstdio>
#include <map>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <queue>

using namespace std;

#define N 100005
#define mod 1000000007
#define ll long long
#define inf 0x3fffffff

char s[N];
int K;
int lef;
char ans[N];
int shang;
int ff;
int l;

void solve()
{
    int i,j,k;
    k = 0;
    for(i = 0;i < shang;i ++){
        j = i;
        //printf(" i = %d\n",i);
        while(j < l){
            //printf("  j = %d l=%d\n",j,l);
            ans[k] = s[j];
            //printf(" j = %d k =%d s= %c ans=%c\n",j,k,s[j],ans[k]);
            k++;
            if(j == ff && lef != 0) break;
            if(j < ff || lef == 0){
                j += shang;
            }
            else{
                j += shang - 1;
            }
        }
    }
    ans[l] = '\0';
}

int main()
{
    int T;
    //freopen("in.txt","r",stdin);
    scanf("%d",&T);
    getchar();
    for(int ccnt = 1;ccnt <= T;ccnt++){
        gets(s);
        scanf("%d",&K);
        getchar();
        l = strlen(s);
        lef = l % K;
        shang = (l + K - 1)/ K;
        ff = lef * shang - 1;
        if(lef == 0) ff = 0;
        //printf(" l = %d lef =%d shang =%d ff =%d\n",l,lef,shang,ff);
        solve();
        printf("Case #%d:\n",ccnt);
        printf("%s\n",ans);
    }
    //freopen("out.txt","w",stdout);

    return 0;
}