There are 4 red, yellow and blue balls in a box, at least how many balls are taken out to ensure that 2 of the taken out balls are of the same color.
一只盒子里有红、黄、蓝三种颜色的小球各4个，至少取出多少个小球，才能保证取出的球中有2个是同色．
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<result>4</result>