UNO plans a gathering.
However there is threat of terrorist attack. So security guard who is a mathematical plans somethings to secure the place.
A terrorist stands nearby the door where
1st ambassador comes , the security guard said 'twelve' and ambassador replied with 'six'.
2nd ambassador comes , the security guard said 'six' and ambassador replied with 'three'.
The terrorist thinks its enough and walks to the door.
The security person said 'eight' , terrorist replied 'four' and get immediately arrested.