foo.cc: In function 'int main()':
foo.cc:6:31: warning: variable 'bn' set but not used [-Wunused-but-set-variable]
  int n,m,a[10000],an,b[10000],bn,c[10000],cn;
                               ^~
foo.cc:6:43: warning: unused variable 'cn' [-Wunused-variable]
  int n,m,a[10000],an,b[10000],bn,c[10000],cn;
                                           ^~

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