There are 4 yellow, red, and green balls of the same size in the box, at least how many balls can be taken out to ensure that there are three colored balls.
箱子里有同样大小的黄、红、绿三种颜色的球各4个，至少取出多少个才能保证有三种颜色的球．
<gadget id="calculator">4 + 4 + 1</gadget>
<output>9</output>

<result>9</result>