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//{

#define FLOAT_PRECISION     2
#define INT_64_MOD          "%I64d"
#define UNSIGNED_64_MOD     "%I64u"

//#pragma comment(linker,"/STACK:102400000,102400000")
#include<cmath>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<algorithm>
#include<bitset>
#include<complex>
#include<vector>
#include<iomanip>
#include<iostream>
#include<list>
#include<map>
#include<queue>
#include<set>
#include<stack>
#include<string>
#define FAST_RW ios_base::sync_with_stdio(0),cin.tie(0);
#define IT(x) __typeof((x).begin())
#define DIT(x) __typeof((x).rbegin())
#define FS(i,a) for(ll i=0;a[i];i++)
#define FE(x,ctn) for(IT(ctn)x=(ctn).begin(),_en=(ctn).end();x!=_en;x++)
#define EF(x,ctn) for(DIT(ctn)x=(ctn).rbegin(),_en=(ctn).rend();x!=_en;x++)
#define FR(i,en) for(ll i=0,_en=(en);i<_en;i++)
#define FOR(i,en) for(ll i=1,_en=(en);i<=_en;i++)
#define RF(i,en) for(ll i=(en)-1;i>=0;i--)
#define ROF(i,en) for(ll i=(en);i>0;i--)
#define FFR(i,x,y) for(ll i=(x),_en=(y);i<=_en;i++)
#define RFF(i,x,y) for(ll i=(x),_en=(y);i>=_en;i--)
#define pc putchar
#define pb push_back
#define pq priority_queue
#define fi first
#define se second
#define mp make_pair
#define pii pair<int,int>
#define pll pair<ll,ll>
#define pdd pair<double,double>
#define lb(x) (x&(-x))
#define sqr(x) ((x)*(x))
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define clr(x) memset((x),0,sizeof(x))
#define ms(x,v) memset((x),(v),sizeof(x))
#define mc(x,y) memcpy((x),(y),sizeof(y))
#define NL puts("");
typedef unsigned ui;
typedef long long ll;
typedef unsigned long long ull;
typedef long double lf;
using namespace std;

ull gcd(ull a,ull b){if(!b)return a;while(b^=a^=b^=a%=b);return a;}

extern const ll MOD;
ll ksm(ll a,ll b){
  ll res=1;
  a%=MOD;
  for(;b;b>>=1){
    if(b&1)res=res*a%MOD;
    a=a*a%MOD;
  }
  return res;
}

#ifdef wmx16835
#include"wmx16835.h"
#else
#define LOG
#define TEL
#define PF
#define PC
#define SF(...)
#define SC
#define test(...) 0
#define TEST(...) 0
#define TRY(...)
#define PP
#define SHOW_TIME
#endif

template<class T1,class T2,class T3>bool In(T1 x,T2 y,T3 z){return x<=y&&x>=z||x<=z&&x>=y;}
template<class T1,class T2>T1 Max(const T1&a,const T2&b){return a<b?b:a;}
template<class T1,class T2,class T3>T1 Max(const T1&a,const T2&b,const T3&c){return a<b?(b<c?c:b):(a<c?c:a);}
template<class T1,class T2>T1 Min(const T1&a,const T2&b){return a<b?a:b;}
template<class T1,class T2,class T3>T1 Min(const T1&a,const T2&b,const T3&c){return a<b?(a<c?a:c):(b<c?b:c);}

bool S(char*a){return scanf("%s",a)==1;}
bool S(int&a){return scanf("%d",&a)==1;}
bool S(bool&a){return scanf("%d",&a)==1;}
bool S(ui&a){return scanf("%u",&a)==1;}
bool S(float&a){return scanf("%f",&a)==1;}
bool S(double&a){return scanf("%lf",&a)==1;}
bool S(ll&a){return scanf(INT_64_MOD,&a)==1;}
bool S(ull&a){return scanf(UNSIGNED_64_MOD,&a)==1;}
bool S(lf&a){double res;if(scanf("%lf",&res)==-1)return 0;a=res;return 1;}
bool S(char&a){char res[2];if(scanf("%1s",res)==-1)return 0;a=*res;return 1;}
bool SL(char*a){a[0]=0;while(gets(a)&&!a[0]);return a[0];}

void _P(const int&x){printf("%d",x);}
void _P(const bool&x){printf("%d",x);}
void _P(const ui&x){printf("%u",x);}
void _P(const char&x){printf("%c",x);}
void _P(const char*x){printf("%s",x);}
void _P(const string&x){printf("%s",x.c_str());}
void _P(const ll&x){printf(INT_64_MOD,x);}
void _P(const ull&x){printf(UNSIGNED_64_MOD,x);}
void _P(const float&x){printf("%.*f",FLOAT_PRECISION,x);}
void _P(const double&x){printf("%.*f",FLOAT_PRECISION,x);}
void _P(const lf&x){printf("%.*f",FLOAT_PRECISION,(double)x);}

template<class T1,class T2>bool S(T1&a,T2&b){return S(a)+S(b)==2;}
template<class T1,class T2,class T3>bool S(T1&a,T2&b,T3&c){return S(a)+S(b)+S(c)==3;}
template<class T1,class T2,class T3,class T4>bool S(T1&a,T2&b,T3&c,T4&d){return S(a)+S(b)+S(c)+S(d)==4;}
template<class T1,class T2,class T3,class T4,class T5>bool S(T1&a,T2&b,T3&c,T4&d,T5&e){return S(a)+S(b)+S(c)+S(d)+S(e)==5;}

template<class T1>void P(const T1&a){_P(a);pc(' ');}
template<class T1,class T2>void P(const T1&a,const T2&b){_P(a);pc(' ');_P(b);pc(' ');}
template<class T1>void PN(const T1&a){_P(a);NL}
template<class T1,class T2>void PN(const T1&a,const T2&b){_P(a);pc(' ');_P(b);NL}
template<class T1,class T2,class T3>void PN(const T1&a,const T2&b,const T3&c){_P(a);pc(' ');_P(b);pc(' ');_P(c);NL}
template<class T1,class T2,class T3,class T4>void PN(const T1&a,const T2&b,const T3&c,const T4&d){_P(a);pc(' ');_P(b);pc(' ');_P(c);pc(' ');_P(d);NL}
template<class T1,class T2,class T3,class T4,class T5>void PN(const T1&a,const T2&b,const T3&c,const T4&d,const T5&e){_P(a);pc(' ');_P(b);pc(' ');_P(c);pc(' ');_P(d);pc(' ');_P(e);NL}
void PS(int a){printf("%*s",a,"");}

template<class T>
void PA(T*a,int n){
  bool f=1;
  FR(i,n){
    if(f)f=0;
    else pc(' ');
    _P(a[i]);
  }
  NL
}

template<class T>
void PA(const T&x){
  bool f=1;
  FE(it,x){
    if(f)f=0;
    else pc(' ');
    _P(*it);
  }
  NL
}

int kase;
const double pi=4*atan(1);
const double ep=1e-9;
const int INF=0x3f3f3f3f;
const ll INFL=0x3f3f3f3f3f3f3f3fll;
const ll MOD=1000000007;
//}

char a[100005],res[100005];

int main(){
  SHOW_TIME
  int T;
  S(T);
  while(T--){
    int n,k;
    SL(a);
    S(k);
    n=strlen(a);
    res[n]=0;
    int x=0,y=0;
    FR(i,n){
      res[x*k+y]=a[i];
      x++;
      if(x*k+y>=n){
        x=0,y++;
      }
    }
    printf("Case #%d:\n",++kase);
    PN(res);
  }
}

/*********Risoft corporation all rights reserved*********/
/**************Template V2.16 build 20150521*************/