tower of hanoi

The Tower of Hanoi or Towers of Hanoi (also known as The 
Towers of Bramha) is a mathematical game or puzzle. It 
consists of three rods, and a number of disks of different 
sizes which can slide onto any rod. The puzzle starts with 
the disks neatly stacked in order of size on one rod, the 
smallest at the top, thus making a conical shape.

The objective of the puzzle is to move the entire stack to 
another rod, obeying the following rules:

-Only one disk may be moved at a time.

-Each move consists of taking the upper disk from one of 
the pegs and sliding it onto another rod, on top of the 
other disks that may already be present on that rod.

-No disk may be placed on top of a smaller disk.
                            source: wikipedia.org