At 1st level, if you take a long rest, do you regain 1 HD back or none?

@dndiy_ft Quick question for you: at 1st level, if you take a long rest. Do you regain 1 HD back or none(from rounding down of .5)? thx! you get 1 – should be min. 1 for long rest

— Mike Mearls (@mikemearls) July 19, 2014