All positive divisors of a positive integer
are written on a blackboard. Two players
and
play the following game taking alternate moves. In the firt move, the player
erases
. If the last erased number is
, then the next player erases either a divisor of
or a multiple of
. The player who cannot make a move loses. Determine all numbers
for which
can win independently of the moves of
.
%V0
All positive divisors of a positive integer $N$ are written on a blackboard. Two players $A$ and $B$ play the following game taking alternate moves. In the firt move, the player $A$ erases $N$. If the last erased number is $d$, then the next player erases either a divisor of $d$ or a multiple of $d$. The player who cannot make a move loses. Determine all numbers $N$ for which $A$ can win independently of the moves of $B$.