/in/foo.cc: In function 'std::vector<int> mul(std::vector<int>, std::vector<int>&)':
/in/foo.cc:7:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < a.size(); i++)
                  ~~^~~~~~~~~~
/in/foo.cc:10:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int j = 0; j < b.size(); j++)
                   ~~^~~~~~~~~~
/in/foo.cc:13:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    if (i + j < ans.size())
        ~~~~~~^~~~~~~~~~~~
/in/foo.cc: In function 'std::vector<int> add(std::vector<int>, std::vector<int>)':
/in/foo.cc:44:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < a.size() || i < b.size(); i++)
                  ~~^~~~~~~~~~
/in/foo.cc:44:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < a.size() || i < b.size(); i++)
                                  ~~^~~~~~~~~~
/in/foo.cc:46:9: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if (i < a.size())t += a[i];
       ~~^~~~~~~~~~
/in/foo.cc:47:9: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if (i < b.size()) t += b[i];
       ~~^~~~~~~~~~