There are several books in class 501, Xiaohong borrowed half of them and more than 1 book, the rest of the book Xiaoming borrowed less than 2 books, which is exactly half, and the remaining books Xiaoying borrowed half of them and more than 3 books, and finally left Next 4 books, how many books did Class 501 originally have.
501班有图书若干本，小红借走了一半多1本，剩下的书小明借走了差2本就正好是一半，再剩下的书小英借走了一半多3本，最后剩下4本书，501班原来有图书多少本．
<gadget id="calculator">4 + 3</gadget>
<output>7</output>

<gadget id="calculator">7 * 2</gadget>
<output>14</output>

<gadget id="calculator">14 - 2</gadget>
<output>12</output>

<gadget id="calculator">12 * 2</gadget>
<output>24</output>

<gadget id="calculator">24 + 1</gadget>
<output>25</output>

<gadget id="calculator">25 * 2</gadget>
<output>50</output>

<result>50</result>