foo.cc: In function 'int main()':
foo.cc:22:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   22 |  int na,nb; scanf("%d%d",&na,&nb);
      |             ~~~~~^~~~~~~~~~~~~~~~
foo.cc:23:31: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   23 |  for(int i=0; i<na; i++) scanf("%d",&a[i]);
      |                          ~~~~~^~~~~~~~~~~~
foo.cc:24:31: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   24 |  for(int i=0; i<nb; i++) scanf("%d",&b[i]);
      |                          ~~~~~^~~~~~~~~~~~

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