foo.cc: In function 'int main()':
foo.cc:36:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   36 |  for(int i=0;i<a.v.size();i++)
      |              ~^~~~~~~~~~~
foo.cc:38:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   38 |   for(int j=0;j<b.v.size();j++)
      |               ~^~~~~~~~~~~

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