/in/foo.cc: In function 'std::vector<int> add(std::vector<int>&, std::vector<int>&)':
/in/foo.cc:14:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < A.size(); i ++ )
                     ~~^~~~~~~~~~
/in/foo.cc:17:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         if (i < B.size()) t += B[i];
             ~~^~~~~~~~~~