Puzzle game 4

                            

Puzzle game 4

You are travelling in the jungles of Africa, when you are caught by a
tribe of barbarians. They allow you to choose between death or solving
their great challenge. You know what you will choose ;)

You are blindfolded and taken to a room, where you are asked to kneel.
You feel hundreds of circular discs lying in front of you. You are told
that one side of each disc is painted red, and the other, green. There
are exactly 129 discs that currently are red side up. You have to
divide the discs into two groups, such that each group has the same
number of discs showing the red colour. Obviously, no peeking allowed.