It was amateur night at Morty's. Alex had finished
his penultimate act of mysterious prestidigitation.
Preparing for the finale, he handed a pile of poker
chips to Jamie and, after turning his back to the
table, asked Jamie to construct three equal stacks
of at least four chips.
Back still to the table, Alex next asked Davey to
call out at random a number between 1 and 12.
Suppose Davey calls out the number x.
With the chips still out of his sight, and without
knowing the number of chips in each stack, Alex
finally gave instructions to Ian to shift chips among
the piles, in a manner that left x chips in the center
What is the method?
To clarify, neither the number x nor the word "all"
were mentioned in the instructions. This rules out
the obvious: move all the chips to stack 3, then
move x of them to the middle.