foo.cc: In function 'int main()':
foo.cc:34:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%lld%lld", &n, &m);
     ~~~~~^~~~~~~~~~~~~~~~~~~~
foo.cc:35:77: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     for (int i = 1; i <= m; i++) scanf("%lld%lld", &x, &y), cd[x]++, rd[y]++, add(x, y);
                                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~

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

{"receive":"2020-05-27T08:52:25.729Z","handle":"2020-05-27T08:52:25.729Z","cache_start":"2020-05-27T08:52:25.735Z","read_cases":"2020-05-27T08:52:25.891Z","judge":"2020-05-27T08:52:25.896Z","done":"2020-05-27T08:52:26.422Z"}