There are 8 red balls, 8 black balls, and 8 white balls in the box. At least how many balls must be drawn to ensure that there are two balls of the same color.
盒子里有红球，黑球，白球各8个，至少摸出多少个球才能保证有两个球的颜色相同．
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<result>4</result>