A new batch of diaries arrived at the stationery store. Last week, the number of diaries sold was 12 less than half of the total number. This week, the number of diaries sold was 12 more than the remaining half. In the end, there were still 19 diaries. How about this batch of diaries? How many?
文化用品店新到一批日记本，上一周售出本数比总数的一半少12本，这一周售出的本数比所剩的一半多12本，结果还有19本，问这批日记本有多少？
<gadget id="calculator">12 + 19</gadget>
<output>31</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">31 / (1/2)</gadget>
<output>62</output>

<gadget id="calculator">62 - 12</gadget>
<output>50</output>

<gadget id="calculator">50 / (1/2)</gadget>
<output>100</output>

<result>100</result>