The number of times the clock strikes at each full hour is equal to the number of hours. If every half hour strikes, how many times does it strike in a month (calculated as 30 days).
时钟在每个整点敲的次数等于钟点数，每半点钟敲一下，一个月(按30天计)共敲多少下．
<gadget id="calculator">1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + 12 + 12</gadget>
<output>90</output>

<gadget id="calculator">90 * 2 * 30</gadget>
<output>5_400</output>

<result>5_400</result>