Circle of death

In the land of Chefton there is a trio of killers known as Team Rocket (TR). Chefton is basically a set of tiles, only a single person can stand on a tile at a given instance. Each tile can be described by X and Y co-ordinates describing the position of the tile. For the purpose of this problem, you may assume that a tile does not have any length of breadth. It is only a point. TR kill in a very