    The Towers of Hanoi is a puzzle consisting of three posts
    and several rings of various sizes.  The initial
    configuration of the game is that all the rings are stacked
    in decreasing order of size on one post.  The object of the
    game is to move all the rings from one post to another
    subject to two rules: only one ring can be moved at a time,
    and at no time can one ring be placed on top of a smaller
    ring.  The number of steps necessary to solve this puzzle is
    exponential in the number rings.
