There are 4 balls of different colors in the cloth bag, each with 10 balls. How many balls must be taken at least to ensure that there must be 3 balls of the same color.
布袋里有4种不同颜色的球，每种都有10个．最少取出多少个球，才能保证其中一定有3个球的颜色一样．
<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">2 * 4</gadget>
<output>8</output>

<gadget id="calculator">8 + 1</gadget>
<output>9</output>

<result>9</result>