+------+ +--------+ +-------+
| Bonn | --> | Berlin | --> | Koeln |
+------+ +--------+ +-------+
^
|
|
+--------+
| Essen |
+--------+
+------+ +--------+ +-------+
| Bonn | --> | Berlin | --> | Koeln |
+------+ +--------+ +-------+
^
|
|
+--------+
| Essen |
+--------+