Xiaojun reads a story book and reads 25 pages a day. After reading it for 5 days, if he reads 4 pages less, he has read half of the book. How many pages is this book?
小军看一本故事书，每天看25页，看了5天后，如果少看4页就正好看了这本书的一半．这本书多少页？
<gadget id="calculator">25 * 5</gadget>
<output>125</output>

<gadget id="calculator">125 - 4</gadget>
<output>121</output>

<gadget id="calculator">121 * 2</gadget>
<output>242</output>

<result>242</result>