/in/foo.cc: In function 'void Div(int, int)':
/in/foo.cc:14:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (i = 0; i < r.size(); ++i)
              ~~^~~~~~~~~~
/in/foo.cc:17:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int j = 0; j < z.size(); ++j) {
                  ~~^~~~~~~~~~