Put 10 balls of each of the five colors of red, yellow, blue, white, and black into a bag. At least how many balls are taken out to ensure that two balls of the same color are taken.
把红、黄、蓝、白、黑五种颜色的球各10个放到一个袋子里．至少取出多少个球，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>