There are 3 white balls and 2 black balls in a box, at least how many balls must be drawn at a time to ensure that there are white balls.
在一个盒了里装有3个白球，2个黑球，一次至少要摸出多少个球，才能保证有白球．
<gadget id="calculator">2 + 1</gadget>
<output>3</output>

<result>3</result>