foo.cc: In function 'int main()':
foo.cc:21:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d%d",&n,&na,&nb);
  ~~~~~^~~~~~~~~~~~~~~~~~~~~
foo.cc:23:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&(ka[i]));
   ~~~~~^~~~~~~~~~~~~~~
foo.cc:25:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&(kb[i]));
   ~~~~~^~~~~~~~~~~~~~~

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