/in/foo.cc: In function 'int itos(std::__cxx11::string)':
/in/foo.cc:5:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<s.length();i++){
              ~^~~~~~~~~~~
/in/foo.cc:8:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int j=0;j<s.length()-1-i;j++){
               ~^~~~~~~~~~~~~~~