/in/foo.cc: In member function 'Big& Big::operator++(int)':
/in/foo.cc:14:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < data.size(); i++)
                   ~~^~~~~~~~~~~~~
/in/foo.cc: In member function 'Big& Big::operator--(int)':
/in/foo.cc:30:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < data.size(); i++)
                   ~~^~~~~~~~~~~~~