/in/foo.cc: In function 'std::vector<int> operator*(std::vector<int>&, std::vector<int>&)':
/in/foo.cc:22:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   22 |     for (int i = 0; i < a.size();i++)
      |                     ~~^~~~~~~~~~
/in/foo.cc:24:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   24 |         for (int j = 0; j < b.size();j++)
      |                         ~~^~~~~~~~~~