foo.cc: In function 'int main()':
foo.cc:13:23: warning: format '%d' expects argument of type 'int', but argument 2 has type 'std::set<int>::size_type {aka long unsigned int}' [-Wformat=]
  printf("%d", s.size());
               ~~~~~~~~^
foo.cc:6:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &n);
  ~~~~~^~~~~~~~~~
foo.cc:8:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d", &x, &y);
   ~~~~~^~~~~~~~~~~~~~~~

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