foo.cc: In function 'int main()':
foo.cc:15:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &n);
  ~~~~~^~~~~~~~~~
foo.cc:17:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d", &a[i].first, &a[i].second); 
   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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