There are 6 red balls, 6 white balls and 6 blue balls, at least how many balls are touched to have 2 balls of the same color.
有6个红球和6个白球和6个蓝球，至少摸多少个球有2个球颜色相同．
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<result>4</result>