/in/foo.cc: In function 'void Output(std::vector<int>&)':
/in/foo.cc:10:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0; i<v.size(); i++)
               ~^~~~~~~~~
/in/foo.cc: In function 'void Sub1(std::vector<int>&, std::vector<int>&)':
/in/foo.cc:17:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0; i<vb.size(); i++)
               ~^~~~~~~~~~