/in/foo.cc: In member function 'void network_flows::set_size_1(int)':
/in/foo.cc:53:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i=0;i<cw.size();i++)
                ~^~~~~~~~~~
/in/foo.cc: In member function 'int network_flows::bfs_1(int, int, double&, double&)':
/in/foo.cc:90:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (int i=0;i<cw[now].size();i++)
                 ~^~~~~~~~~~~~~~~