#include <queue>
#include <vector>
#include <string>
#include <iostream>
#include <algorithm>
using namespace std;
const int max_len = 100000 + 10;
vector<vector<int> > v;
int main() {
    ios::sync_with_stdio(false);
    cin.tie(NULL);
    int T;
    cin >> T;
    cin.ignore();
    for(int kcase = 1; kcase <= T; kcase++) {
        string str;
        getline(cin , str);
        int K , len = str.size();
        cin >> K;
        cin.ignore();
        int r = (len/K)+(len%K != 0) , c = K;
        v = vector<vector<int> >(r , vector<int>(c , 0));
        int tmp = r*c - len;
        for(int i = r-1; i >= 0 && tmp > 0; i--) {
            for(int j = c-1; j >= 0 && tmp > 0; j--) {
                v[i][j] = -1;
                tmp--;
            }
        }
        int ptr = 0;
        for(int j = 0; j < c; j++) {
            for(int i = 0; i < r; i++) {
                if(!v[i][j]) {
                    v[i][j] = str[ptr++];
                }
            }
        }
        cout << "Case #" << kcase << ':' << endl;
        int flag = 0;
        for(int i = 0; i < r; i++) {
            for(int j = 0; j < c; j++) {
                if(v[i][j] == -1) {
                    flag = 1;
                    break;
                }
                else cout << (char)v[i][j];
            }
            if(flag) break;
        }
        cout << endl;
    }
    return 0;
}