/in/foo.cc: In function 'void Add(std::vector<Poly>&, std::vector<Poly>&)':
/in/foo.cc:42:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0; i<L2.size(); i++)
               ~^~~~~~~~~~
/in/foo.cc: In function 'void Output(std::vector<Poly>&)':
/in/foo.cc:50:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0; i<L.size()&&L[i].coef!=0; i++)
               ~^~~~~~~~~
/in/foo.cc: In function 'int Insert(std::vector<Poly>&, int, Poly&)':
/in/foo.cc:34:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^