[ Bonn ] --> [ Berlin ] --> [ Frankfurt ]
[ Bonn ] --> [ Berlin ] --> [ Bonn ]
[ Ulm ] --> [ Berlin ] --> [ Berlin ]
[ Mainz ] --> [ Bonn ]
[ Bonn ] --> [ Berlin ] --> [ Frankfurt ]
[ Bonn ] --> [ Berlin ] --> [ Bonn ]
[ Ulm ] --> [ Berlin ] --> [ Berlin ]
[ Mainz ] --> [ Bonn ]