#include <cstdio>
#include <cstring>

const int MAXN = 10e5;
char str[MAXN+5];
char cip[MAXN+5];

int main()
{
    int t, key;
    size_t len;
    int rest, row;
    int cnt;
    
    scanf("%d", &t);
    getchar();
    
    for(int i = 1; i <= t; i++) {
        gets(str);
        scanf("%d", &key);
        getchar();
        
        cnt = 0;
        len = strlen(str);
        rest = len % key;
        row = len/key + 1;
        
        for(int j = 0; j < rest; j++) {
            for(int k = 0; k < row; k++) {
                cip[k*key+j] = str[cnt++];
            }
        }
        
        for(int j = rest; j < key; j++) {
            for(int k = 0; k < row - 1; k++) {
                cip[k*key+j] = str[cnt++];
            }
        }
        
        printf("Case #%d:\n", i);
        for (int i = 0; i < len; i++) {
            putchar(cip[i]);
        }
        putchar('\n');
    }
    
    return 0;
}