There are probably much easier solutions,
but workaround for that could be something like this:
Give the character an instance variable "number"
character on created
> character set variable "number" = character.count
character on destroyed
pick all characters
(- for each character)
> character set variable "number" - character.number-1
on x pressed
system pick by comparison - character.number = 1
> character destroy
I told my dentist I had trouble with my teeth and asked her to fix it without looking in my mouth..