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