foo.cc: In function 'int main()':
foo.cc:73:11: warning: variable 'tmp' set but not used [-Wunused-but-set-variable]
     qnode tmp = q.top();
           ^~~
foo.cc:58:6: warning: unused variable 'ans' [-Wunused-variable]
  int ans;
      ^~~

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