foo.cc: In function 'int main()':
foo.cc:5:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d%d%d",&n,&m,&b,&c);
  ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

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

{"receive":"2020-08-12T12:03:04.773Z","handle":"2020-08-12T12:03:04.773Z","cache_start":"2020-08-12T12:03:04.780Z","read_cases":"2020-08-12T12:03:04.909Z","judge":"2020-08-12T12:03:04.912Z","done":"2020-08-12T12:03:05.065Z"}