foo.cc: In function 'int main()':
foo.cc:11:6: warning: unused variable 'b' [-Wunused-variable]
  int b[1000];
      ^
foo.cc:13:6: warning: unused variable 'cnt' [-Wunused-variable]
  int cnt=0;
      ^~~

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