Put 8 balls of red, yellow, blue, and white colors into a bag. At least how many balls must be taken to ensure that two balls of the same color are taken.
把红、黄、蓝、白四种颜色的球各8个放到一个袋子里．至少要取多少个球，才可以保证取到两个颜色相同的球．
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<result>5</result>