/in/foo.cc: In function 'int main()':
/in/foo.cc:28:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<p.size();i++){
              ~^~~~~~~~~
/in/foo.cc:29:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   std::cout<<p[i]<<" \n"[i==p.size()-1];
                          ~^~~~~~~~~~~~