Railroad enthusiasts are numerous and active. They ride trains, visit stations, create models of rail systems
and use software to simulate trains and rail systems. One of the favorite areas of a rail system for many
enthusiasts is the “switching yard” or “roundhouse” where engines and rail cars are assembled into trains
and sent out on various errands. Your assignment will be to create a program that allows the user to
assemble rail cars into trains of cars of the correct order using a simple switching yard.