/in/foo.cc: In function 'int selete(bool*, std::vector<int>&)':
/in/foo.cc:7:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<a.size();i++)
              ~^~~~~~~~~
/in/foo.cc:18:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<a.size();i++)
              ~^~~~~~~~~
/in/foo.cc:29:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<a.size();i++)
              ~^~~~~~~~~