Put 20 balls of red, white, and blue colors into a bag, and take at least how many balls to ensure that you get two balls of the same color.
把红、白、蓝三种颜色的球各20个放到一个袋子里，至少取多少个球，可以保证取到两个颜色相同的球．
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<result>4</result>