#include <iostream>
#include <cstdio>
#include <cstring>

using namespace::std;

const int maxn = 1e5 + 10;
int t, n, len, k;
char s[maxn], p[maxn];

void GetLine(char *s)
{
    char ch;
    while ((ch = getchar()) == '\n');
    s[0] = ch;
    int cnt = 1;
    while ((ch = getchar()) != '\n')
    {
        s[cnt++] = ch;
    }
    s[cnt] = '\0';
}

int main()
{
    cin >> t;
    int a = 1;
    while (t--)
    {
        GetLine(s);
        scanf("%d", &n);
        len = strlen(s);
        k = len / n;
        int cnt = 0;
        for (int i = 0; i < n; i++)
            for (int j = 0; i + j * n < len; j++)
            {
                p[i + j * n] = s[cnt++];
            }
        p[len] = '\0';
        printf("Case #%d:\n%s\n", a++, p);
    }
    return 0;
}