foo.cc: In function 'void work()':
foo.cc:18:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<ex.size();i++)
              ~^~~~~~~~~~
foo.cc: In function 'bool check(long long int, long long int)':
foo.cc:43:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<ed[k].size();i++)
               ~^~~~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:73:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int j=0;j<e0[a].size();j++)
                 ~^~~~~~~~~~~~~
foo.cc:83:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int j=0;j<e1[x].size();j++)
                ~^~~~~~~~~~~~~
foo.cc:52:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%lld%lld%lld",&n,&m,&q);
  ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:56:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%lld%lld",&x,&y);
   ~~~~~^~~~~~~~~~~~~~~~~~
foo.cc:66:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%lld",&op);
   ~~~~~^~~~~~~~~~~~
foo.cc:70:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%lld%lld",&a,&b);
    ~~~~~^~~~~~~~~~~~~~~~~~
foo.cc:81:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%lld",&x);
    ~~~~~^~~~~~~~~~~

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