IMO Shortlist 2004 problem C5
Dodao/la:
arhiva2. travnja 2012. 3.

and

play a game, given an integer

,

writes down

first, then every player sees the last number written and if it is

then in his turn he writes

or

, but his number cannot be bigger than

. The player who writes

wins!, For wich values of

does

wins?
%V0
3. $A$ and $B$ play a game, given an integer $N$, $A$ writes down $1$ first, then every player sees the last number written and if it is $n$ then in his turn he writes $n+1$ or $2n$, but his number cannot be bigger than $N$. The player who writes $N$ wins!, For wich values of $N$ does $B$ wins?
Izvor: Međunarodna matematička olimpijada, shortlist 2004