Here you see a small shunting-yard with two wagons (blue and green) and one locomotive (red).

The wagons have a length of 5 meters, and the locomotive has a length of 10 meters. The dead end between the buffer-stop and the switch on the lower left has a length of 5 meters (so the locomotive cannot change tracks on the lower left switch), and the dead end between the switch and the buffer-stop on the lower right has a length of 15 meters. The locomotive can move forward and backward, and can both pull and push wagons.

The question: How must the locomotive shunt the wagons, to arrive in a situation where the wagons have changed places and the locomotive is back in its starting position?

The answer: Click here!