There are 3 red balls and 3 yellow balls of the same size in the box. If you want to draw out the balls, there must be 2 of the same color. The minimum number of balls must be drawn out.
盒子里有同样大小的红球、黄球各3个，要想摸出的球一定有2个是同色的，最少要摸出多少个球．
<gadget id="calculator">2 + 1</gadget>
<output>3</output>

<result>3</result>