Ding Ding reads a book of "Children's Literature", and reads an average of 28 pages a day. After 4 days, he reads 15 pages, which is exactly half of the book. How many pages does this "Children's Literature" have in total?
丁丁看一本《儿童文学》，平均每天看28页，看了4天后，再看15页就正好是这本书的一半，这本《儿童文学》一共有多少页？
<gadget id="calculator">28 * 4</gadget>
<output>112</output>

<gadget id="calculator">112 + 15</gadget>
<output>127</output>

<gadget id="calculator">127 * 2</gadget>
<output>254</output>

<result>254</result>