/in/foo.cc: In function 'std::vector<int> times(std::vector<int>&, std::vector<int>&)':
/in/foo.cc:8:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int b_pos=0;b_pos<b.size();b_pos++){
                  ~~~~~^~~~~~~~~
/in/foo.cc:10:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int a_pos=0;a_pos<a.size();a_pos++){
                   ~~~~~^~~~~~~~~
/in/foo.cc:12:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    if(a_pos+b_pos>=c.size()) c.push_back(t%10);
       ~~~~~~~~~~~^~~~~~~~~~