/in/foo.cc: In function 'CG::Segments solve::the_next(CG::Segments)':
/in/foo.cc:99:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < sg.size(); ++i)
                   ~~^~~~~~~~~~~
/in/foo.cc: In function 'void solve::solve()':
/in/foo.cc:134:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < sg.size(); ++i) 
                   ~~^~~~~~~~~~~
/in/foo.cc:157:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < res.size(); ++i) cout << res[i] << " ";
                   ~~^~~~~~~~~~~~