foo.cc: In function ‘std::vector<int> Union(std::vector<int>&, std::vector<int>&)’:
foo.cc:9:18: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<int>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
    9 |         while (i < va.size() && j < vb.size())
      |                ~~^~~~~~~~~~~
foo.cc:9:35: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<int>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
    9 |         while (i < va.size() && j < vb.size())
      |                                 ~~^~~~~~~~~~~
foo.cc:29:18: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<int>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   29 |         while (i < va.size())
      |                ~~^~~~~~~~~~~
foo.cc:34:18: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<int>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   34 |         while (j < vb.size())
      |                ~~^~~~~~~~~~~
foo.cc: In function ‘void Output(std::vector<int>&)’:
foo.cc:43:27: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<int>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   43 |         for (int i = 0; i < vc.size(); i++) cout << vc[i] << " ";
      |                         ~~^~~~~~~~~~~