There are 10 red and white ping-pong balls of the same size in the bag. If you want to draw out the balls, there must be 2 of the same color. At least how many balls must be drawn out.
袋子里由同样大小的红色和白色的乒乓球各10个，要想摸出的球一定有2个同色的，至少要摸出多少个球．
<gadget id="calculator">2 + 1</gadget>
<output>3</output>

<result>3</result>