There are 3 yellow, blue, and red balls in the bag, reach into the bag, and take at least how many balls to ensure that you get 2 balls of the same color.
袋子里放了黄色、蓝色、红色的球各3个，把手伸到袋子里，最少拿多少个球，才能保证拿到2个相同颜色的球．
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<result>4</result>