/in/foo.cc: In function 'void num_to_fraction(std::__cxx11::string)':
/in/foo.cc:69:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < s.length(); i++)
                  ~~^~~~~~~~~~~~
/in/foo.cc:77:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (i = 0; i < num.length(); i++)
              ~~^~~~~~~~~~~~~~