foo.cc: In function 'int main()':
foo.cc:16:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   16 |     for (int i=0; i<b_num.size(); i++){
      |                   ~^~~~~~~~~~~~~
foo.cc:21:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   21 |     for (int i=0; i<a.size(); i++){
      |                   ~^~~~~~~~~

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