There are 8 red balls and 8 white balls of the same size in the box. If you want to draw balls, there must be 2 of the same color. At least how many balls must be drawn.
盒子里有同样大小的红球和白球各8个，要想摸出的球一定有2个是同色的，至少要摸出多少个球．
<gadget id="calculator">2 + 1</gadget>
<output>3</output>

<result>3</result>