foo.cc: In function 'int main()':
foo.cc:11:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d%d",&n,&m,&p);
     ~~~~~^~~~~~~~~~~~~~~~~~~
foo.cc:12:34: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     for(int i=1; i<=n; ++i) scanf("%d%d",&x[i],&y[i]);
                             ~~~~~^~~~~~~~~~~~~~~~~~~~
foo.cc:21:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d%d",&a,&b,&c);
         ~~~~~^~~~~~~~~~~~~~~~~~~

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