foo.cc: In function 'int main()':
foo.cc:12:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%lf",&n,&r);
  ~~~~~^~~~~~~~~~~~~~~
foo.cc:15:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%lf%lf",&x1,&y1);
  ~~~~~^~~~~~~~~~~~~~~~~~
foo.cc:20:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%lf%lf",&x2,&y2);
   ~~~~~^~~~~~~~~~~~~~~~~~

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。