Question 63
Natural numbers $1$ through $n$ are written on a blackboard. On each move, one erases from the blackboard $2$ or more numbers whose sum is divisible by any of the chosen numbers and writes their sum on the blackboard. Two players make moves by turns and the player who cannot move loses the game. Which player can win the game against any play by the opponent, if:
a. $n = 6$;
b. $n = 11$?
a. $n = 6$;
b. $n = 11$?