/in/foo.cc: In function 'std::__cxx11::string div(std::__cxx11::string, int)':
/in/foo.cc:13:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<a.length();i++){
                 ~^~~~~~~~~~~
/in/foo.cc:18:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<r.length();i++)
                 ~^~~~~~~~~~~