foo.cc:4:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main()
      ^
foo.cc: In function 'int main()':
foo.cc:10:37: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   cin>>x; for(int i=1;i<=x;++i)scanf("%d",&a[i]);
                                ~~~~~^~~~~~~~~~~~
foo.cc:11:37: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   cin>>y; for(int i=1;i<=y;++i)scanf("%d",&b[i]);
                                ~~~~~^~~~~~~~~~~~

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