There are 500 beads in a pocket, there are 5 colors, 100 each, if you close your eyes, how many beads should you take out at least to ensure that 5 of them are the same? Why?
一个口袋中装有500粒珠子，共有5种颜色，各100颗，如果你闭上眼睛在，至少取出多少粒珠子才能保证其中有5粒相同？为什么？
<gadget id="calculator">4 * 5</gadget>
<output>20</output>

<gadget id="calculator">20 + 1</gadget>
<output>21</output>

<result>21</result>