There are several yellow, blue, and red balls in the bag. Put your hand 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、红色的球若干个，把手伸进袋子里，最少拿多少个球，才能保证拿到2个颜色相同的球．
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<result>4</result>