There are 4 red balls and 4 blue balls of the same size in the box. If you want to draw out the balls, there must be 2 of different colors. What is the minimum number of balls you need to draw out?
盒子里有同样大小的红色、蓝色的球各4个，要想摸出的球中一定有2个是不同色的，最少要摸出多少个球．
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<result>5</result>