foo.cc: In function 'int main()':
foo.cc:45:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  int n; scanf("%d", &n);
         ~~~~~^~~~~~~~~~
foo.cc:48:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d", &x, &y);
   ~~~~~^~~~~~~~~~~~~~~~
foo.cc:51:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  int m; scanf("%d", &m);
         ~~~~~^~~~~~~~~~
foo.cc:71:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d", &x, &y);
   ~~~~~^~~~~~~~~~~~~~~~

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

Cannot connect to sandbox service 
Error: Cannot connect to sandbox service 
    at run (/root/HydroJudger/judge/sandbox.js:93:15)
    at process._tickCallback (internal/process/next_tick.js:68:7)
"Request failed with status code 500"