[Hoagy]

Wow, that is very counterintuitive..

I suppose you could set any threshold x, and play so that if the first number is bigger than x you stick, otherwise you switch. This would be strictly better than random (break even) if x is within the range of numbers that A is picking from and the same as random if not.

It depends on when you measure your chances: before A has picked a generator this gives you >50% chance but if A has already picked a range to draw from that doesn't contain x then you're back to 50/50. Still, I think this would count as guaranteeing >50%?