POJ 2610

 #include<iostream>
 #include<iomanip>
 using namespace std;

 int main()
 {
     //freopen("acm.acm","r",stdin);
     double x1;
     double y1;
     double x2;
     double y2;
     double hol_x;
     double hol_y;
     double len_gop;
     double len_dog;
     bool boo = false;
     cin>>x1>>y1>>x2>>y2;
     while(cin>>hol_x>>hol_y)
     {
         len_gop = (x1-hol_x)*(x1-hol_x) + (y1-hol_y)*(y1-hol_y);
         len_dog = (x2-hol_x)*(x2-hol_x) + (y2-hol_y)*(y2-hol_y);
         if(len_dog/4.000 > len_gop)
         {
             cout<<"The gopher can escape through the hole at ("<<setiosflags(ios::fixed)<<setprecision()<<hol_x<<","<<hol_y<<")."<<endl;
             boo = true;
             break;
         }
     }
     if(!boo)
         cout<<"The gopher cannot escape."<<endl;
 }