foo.cc: In function 'int main()':
foo.cc:8:16: warning: unused variable 'b' [-Wunused-variable]
  int a[100001],b[100000];
                ^
foo.cc:11:6: warning: unused variable 'i' [-Wunused-variable]
  int i=0;
      ^

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