Put 10 balls of each color in a bag, and at least 5 balls must be taken out to ensure that two balls of the same color are taken.
把多少种颜色的球各10个放在一个袋子里，至少要取出5个球，可以保证取到两个颜色相同的球．
<gadget id="calculator">5 - 1</gadget>
<output>4</output>

<result>4</result>