/in/foo.cc: In function 'std::vector<int> Mul(std::vector<int>&, int)':
/in/foo.cc:15:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < a.size(); ++i) {
                     ~~^~~~~~~~~~
/in/foo.cc:33:35: error: 'reverse' was not declared in this scope
     reverse(res.begin(), res.end());
                                   ^