Donate books to schools in Wenchuan earthquake-stricken areas, 50 books are packed into a pack, and the first primary school is only 7 books short of 39 packs. How many books did No.1 Primary School donate?
为汶川地震灾区学校捐赠图书，50本包成一包，第一小学还差7本就够39包．第一小学捐了多少本图书？
<gadget id="calculator">39 * 50</gadget>
<output>1_950</output>

<gadget id="calculator">1_950 - 7</gadget>
<output>1_943</output>

<result>1_943</result>