Two trains, one of an engine and a car and another - of an engine and two cars, meet at a segment of railroad. There is a switch or side-track on that segment of railroad - just as shown in the illustration. The switch is large enough only to hold one engine or one car at a time.

The object is, using only this switch, to exchange the trains in order they can continue their journeys and do that in the most expeditious way. No other outside help, except the switch itself, is allowed. Please, note that a car cannot be connected to the front of an engine.
 

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