#include <iostream>

#include <cstdio>

#include <sstream>

#include <cstring>

#include <map>

#include <set>

#include <vector>

#include <stack>

#include <queue>

#include <algorithm>

#include <cmath>

#define MOD 2018

#define LL long long

#define ULL unsigned long long

#define Pair pair<int, int>

#define mem(a, b) memset(a, b, sizeof(a))

#define _  ios_base::sync_with_stdio(0),cin.tie(0)

//freopen("1.txt", "r", stdin);

using namespace std;

const int maxn = , INF = 0x7fffffff;

set<LL> s;

int main()

{

    int T, kase = ;

    scanf("%d",&T);

    while(T--)

    {

        s.clear();

        LL p, l;

        scanf("%lld%lld",&p,&l);

        for(LL i=; i * i<=p-l; i++)

            if((p-l)%i == )

            {

                if(i > l)

                    s.insert(i);

                if((p-l)/i > l)

                    s.insert((p-l)/i);

            }

        printf("Case %d:",++kase);

        if(s.empty())

            printf(" impossible");

        else

            for(set<LL>::iterator it = s.begin(); it!=s.end(); it++)

            {

                printf(" ");

                printf("%lld",*it);

            }

        printf("\n");

    }

    return ;

}