A pocket contains 8 balls of three different colors, red, yellow, and blue. At least how many balls must be drawn to ensure that there are 8 balls of the same color.
一个口袋里装有红、黄、蓝三种不同颜色的小球各8个，至少要摸出多少个小球，才能保证有8个颜色相同的小球．
<gadget id="calculator">7 * 3</gadget>
<output>21</output>

<gadget id="calculator">21 + 1</gadget>
<output>22</output>

<result>22</result>