foo.cc: In function 'int main()':
foo.cc:13:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d" ,&n ,&k);
  ~~~~~^~~~~~~~~~~~~~~~~
foo.cc:15:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d" ,&a[i]);
   ~~~~~^~~~~~~~~~~~~
foo.cc:18:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d" ,&b[j]);
   ~~~~~^~~~~~~~~~~~~

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