theoretical heads-up question

[ezratei]

you are playing a NLHE shoot-out heads up against a computer. You can only play one shoot-out and then the computer will explode. The computer is programmed to go all-in preflop every hand. Blinds are $0.5/$1. You both start with stack-size $X.

First hand: You are BB and dealt KK ... computer goes all-in.

At what stack-size X is folding correct?