/in/foo.cc: In function 'void SetInter(std::vector<int>, std::vector<int>)':
/in/foo.cc:6:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<a1.size();i++)
              ~^~~~~~~~~~
/in/foo.cc:7:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int j=0;j<a2.size();j++)
                 ~^~~~~~~~~~