There are 3 red balls and 4 white balls in the box, at least how many balls must be drawn to ensure that there are two of the same color.
箱子里有3个红球、4个白球，至少摸出多少个球，才能保证有两个颜色相同．
<gadget id="calculator">2 + 1</gadget>
<output>3</output>

<result>3</result>