foo.cc: In function 'int main()':
foo.cc:13:6: warning: unused variable 'c' [-Wunused-variable]
  int c[20000];
      ^
foo.cc:14:6: warning: unused variable 'cnt' [-Wunused-variable]
  int cnt=0; 
      ^~~
foo.cc: In function 'void Find2(int*, int*, int, int)':
foo.cc:36:6: warning: variable 'c' set but not used [-Wunused-but-set-variable]
  int c[n3];
      ^
foo.cc: In function 'int Find(int*, int*, int, int)':
foo.cc:30:1: 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。