/in/foo.cc: In function 'void Output(std::vector<int>&)':
/in/foo.cc:9:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0; i<a.size(); i++)
               ~^~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:24:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=1; i<a.size(); i++)
               ~^~~~~~~~~