+---+
| 1 | -----------+
+---+ v
+---+----+ +---+
| 2 | 3 | --> | 3 |
+---+----+ +---+
+---+
| 1 | -----------+
+---+ v
+---+----+ +---+
| 2 | 3 | --> | 3 |
+---+----+ +---+