There are 10 red, yellow, and blue balls in a pocket, at least how many balls can be drawn to ensure that there are 10 balls of the same color.
一个口袋里有红黄蓝三种不同颜色的小球各10个，至少摸出多少个小球才能保证有10个颜色相同．
<gadget id="calculator">9 * 3</gadget>
<output>27</output>

<gadget id="calculator">27 + 1</gadget>
<output>28</output>

<result>28</result>