http://acm.hdu.edu.cn/contests/contest_showproblem.php?pid=1005&cid=867

#include
#include
#include
#include
#include
using namespace std;
int main(){
int t;
scanf("%d",&t);
int sign=;
while(t--){
double r,h;
scanf("%lf%lf",&r,&h);
double tanx=h/r;
double x0,y0,z0,xv,yv,zv;
scanf("%lf%lf%lf%lf%lf%lf",&x0,&y0,&z0,&xv,&yv,&zv);
double a=xv*xv+yv*yv-zv*zv/(tanx*tanx);
double b=2.0*(x0*xv+y0*yv+zv*r/tanx-z0*zv/(tanx*tanx));
double c=x0*x0+y0*y0-r*r+2.0*z0*r/tanx-z0*z0/(tanx*tanx);
double fuck=fabs(b*b-4.0*a*c);
double ans1=(-b+sqrt(fuck))/(2.0*a);
double ans2=(-b-sqrt(fuck))/(2.0*a);
double ans;
double z1=z0+zv*ans1;
double z2=z0+zv*ans2;
if(z1<=h&&z1>=&&z2<=h&&z2>=){
ans=min(ans1,ans2);
}
else if(z1<=h&&z1>=){
ans=ans1;
}
else
ans=ans2;
printf("Case %d: %.10lf\n",sign++,ans);
}
return ;
}