#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstring>
#include<algorithm>
using namespace std;
#define MAX 1000005
#define pf printf
#define sf scanf
typedef long long ll;
ll a[MAX];
int main()
{
ll p, l, sub;
int test, t;
sf("%d", &test);
for(t=1; t<=test; t++)
{
sf("%lld%lld", &p, &l);
sub = (p-l);
pf("Case %d:", t);
if(sub<=l)
{
pf(" impossible\n");
}
else
{
int k=1;
int count = 0;
int temp = sqrt(sub);
for(int i=1; i<=temp; i++)
{
if(sub%i==0)
{
ll div = (sub/i);
if(div>l)
{
a[k] = div;
k++;
count++;
}
if(i>l && div!=i )
{
a[k] = i;
k++;
count++;
}
}
}
sort(a, a+k);
for(int j=1; j<=count; j++)
{
pf(" %lld", a[j]);
}
pf("\n");
}
}
}