#include<bits/stdc++.h>
using namespace std;

int main()
{
    int n,r,i=0,j,k,s,a,b,c,d,e;
    while(cin>>r>>n)
    {

        if(r==0||n==0)
            break;
      r--;
       a=(r/n);
       if(a>26)
        cout<<"Case "<<++i<<": "<<"impossible"<<endl;
       else
        cout<<"Case "<<++i<<": "<<a<<endl;
    }
    return 0;
}