foo.cc: In function 'int main()':
foo.cc:16:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d%d%d", &n, &m, &x, &y);
  ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

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

{"receive":"2020-08-16T16:49:06.387Z","handle":"2020-08-16T16:49:06.388Z","cache_start":"2020-08-16T16:49:06.394Z","read_cases":"2020-08-16T16:49:06.525Z","judge":"2020-08-16T16:49:06.528Z","done":"2020-08-16T16:49:07.019Z"}