foo.cc: In function 'int main()':
foo.cc:6:6: warning: unused variable 'aa' [-Wunused-variable]
  int aa=a,bb=b;
      ^~
foo.cc:6:11: warning: unused variable 'bb' [-Wunused-variable]
  int aa=a,bb=b;
           ^~

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