foo.cc: In function 'int main()':
foo.cc:43:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%lld", &n);
  ~~~~~^~~~~~~~~~~~
foo.cc:45:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%lld", &a[i]);
   ~~~~~^~~~~~~~~~~~~~~
foo.cc:48:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%lld", &b[i]);
   ~~~~~^~~~~~~~~~~~~~~