# node lists on the left side
[ Ulm ], [ Hahn ], [ Wismar ] => [ Frankfurt ]
[ Frankfurt ] -> [ Potsdam ]
[ Frankfurt ], [ Lahn ] -> [ Potsdam ]
# node lists on the left side
[ Ulm ], [ Hahn ], [ Wismar ] => [ Frankfurt ]
[ Frankfurt ] -> [ Potsdam ]
[ Frankfurt ], [ Lahn ] -> [ Potsdam ]