/in/foo.cc: In function 'int get_mod(std::__cxx11::string, int)':
/in/foo.cc:8:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<str.size();++i)
                 ~^~~~~~~~~~~
/in/foo.cc: In function 'std::__cxx11::string div(std::__cxx11::string, int)':
/in/foo.cc:18:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<str.size();++i)
                 ~^~~~~~~~~~~
/in/foo.cc:24:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<r.size();++i)
                 ~^~~~~~~~~
/in/foo.cc: In function 'bool iszero(std::__cxx11::string)':
/in/foo.cc:34:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<str.size();++i)
                 ~^~~~~~~~~~~