It is obvious that for the first player (A) to win he must remove, in the

It is obvious that for the first player (A) to win he must remove, in the first step, less than 6 pebbles (as
he is not allowed to remove all the 12 pebbles).
So the number of pebbles A can remove in order to win will be 2,3,4 ,5.
Removing 1 pebble by A, in the first step, will ensure that B is the winner.
A will win, after B removes his pebbles, each time the number of the remaining pebbles will be 5 or 6.
From such a position A always win as shown below. The game is “don’t be greedier”
left A left B left A left B left A left B left A left A
5
1 4
1 3 1
2 1 1
6
2 4
2 2 2 0
6
2 4
1 3 1
2 1
1 0
A WINS
A WINS
1
1 0
A WINS
The position of 5 or 6 remaining pebbles can occur at any step during the play.