[ Bonn ] -> [ Berlin ]
[ Berlin ] -> [ Frankfurt ]
[ Frankfurt ] -> [ Dresden ]
[ Berlin ] -> [ Potsdam ]
[ Potsdam ] -> [ Cottbus ] { border-color: red; }
[ Cottbus ] -> [ Frankfurt ]
[ Bonn ] -> [ Berlin ]
[ Berlin ] -> [ Frankfurt ]
[ Frankfurt ] -> [ Dresden ]
[ Berlin ] -> [ Potsdam ]
[ Potsdam ] -> [ Cottbus ] { border-color: red; }
[ Cottbus ] -> [ Frankfurt ]