There are 15 matches. A and B take turns to get the matches. Each time they can only get 1 or 2 matches. Whoever gets the last one will win. In order to ensure victory, how should B get the matches?
有15根火柴，甲，乙两人轮流取火柴，每次只能取1根或2根，谁取到最后一根谁能赢．为了确保获胜，乙应该怎样取火柴？
<gadget id="calculator">15 - 3 - 3 - 3 - 3</gadget>
<output>3</output>

<result>3</result>