+--------+-----------+
| bonn N | S | -+
+--------+-----------+ |
| |
+---------+ |
| v
| +----------+----+
+-----> | berlin N | w |
+----------+----+
+--------+-----------+
| bonn N | S | -+
+--------+-----------+ |
| |
+---------+ |
| v
| +----------+----+
+-----> | berlin N | w |
+----------+----+