#include<stdio.h>
int main()
{
    long long  i,n,r,k;
    for(i=1;i<=10002;i++)
    {
        scanf("%lld%lld",&r,&n);
        if((r==0)&&(n==0))
        {
            break;
        }
        else
        {
            k=(r-1)/n;
            if(k>26)
            {
                printf("Case %lld: impossible\n",i);
            }
            else
            {
                printf("Case %lld: %lld\n",i,k);
            }
        }
    }

}