foo.cc: In function 'int main()':
foo.cc:8:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf ("%d", &n);
  ~~~~~~^~~~~~~~~~
foo.cc:10:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf ("%d", &a);
   ~~~~~~^~~~~~~~~~

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

{"receive":"2020-07-19T10:07:38.716Z","handle":"2020-07-19T10:07:38.716Z","cache_start":"2020-07-19T10:07:38.722Z","read_cases":"2020-07-19T10:07:38.855Z","judge":"2020-07-19T10:07:38.857Z","done":"2020-07-19T10:07:39.214Z"}