You have three small poles and five hoops - XS, S, M, L, XL (as in extra small, small, medium, large and extra large). They are placed on pole 1 in order, with largest at the bottom.
You can move one hoop at a time, and the hoops you are not moving have to be on a pole. You also cannot place a hoop on top of a smaller one. How can you move the hoops so that they are in the same order as they are now, but on pole 3?
If the hoops are colored with alternating colors (XS, M, XL are one color and S, L are a second), then every move either places a hoop on an empty stack or on a hoop of the opposite color.