foo.cc: In function 'int main()':
foo.cc:53:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%lld",&n);
  ~~~~~^~~~~~~~~~~
foo.cc:56:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%lld",&a[i]);
  ~~~~~^~~~~~~~~~~~~~
foo.cc:58:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%lld",&b[i]);
  ~~~~~^~~~~~~~~~~~~~