foo.cc: In function 'int main()':
foo.cc:26:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   26 |  for(int i=0; i<vb.size(); i++)
      |               ~^~~~~~~~~~
foo.cc:29:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   29 |  for(int i=0; i<vc.size(); i++)
      |               ~^~~~~~~~~~

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