foo.cc: In function 'int main()':
foo.cc:30:7: warning: unused variable 'x' [-Wunused-variable]
   int x=0;
       ^
foo.cc: In function 'bool A(student, student)':
foo.cc:22:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^

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