book of fairy tales has a total of 600 pages, numbered 1, 2, 3, 4, ... 599, 600. Ask how many times the number "2" appears in the page number.
一本童话故事书共600页，编上页码1、2、3、4、…599、600．问数字"2"在页码中一共出现了多少次．
<gadget id="calculator">100 + 20</gadget>
<output>120</output>

<gadget id="calculator">3 * 20</gadget>
<output>60</output>

<gadget id="calculator">20 + 20 + 120 + 60</gadget>
<output>220</output>

<result>220</result>