There are 4 red balls and 4 blue balls of the same size in the box. There must be 2 balls of the same color to be drawn. How many balls must be touched at least.
盒子里有同样大小的红球和蓝球各4个，想要摸出的球一定有两个同色的，最少要摸多少个球．
<gadget id="calculator">2 + 1</gadget>
<output>3</output>

<result>3</result>