Lingling has a lot of extracurricular books, Pengpeng borrowed half of them plus 1 book, Nan Nan borrowed half of the remaining books plus 2 books, and Qingqing borrowed half of the remaining books plus 3 books, and finally, Lingling returned There are 12 extracurricular books, do you know how many extracurricular books Lingling originally had?
玲玲有许多课外书，鹏鹏借走了一半加1本，剩下的书，楠楠借走了一半加2本，再剩下的书，青青借走了一半加3本，最后，玲玲还有12本课外书，你知道玲玲原来有多少本课外书？
<gadget id="calculator">12 + 3</gadget>
<output>15</output>

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

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

<gadget id="calculator">15 / (1/2)</gadget>
<output>30</output>

<gadget id="calculator">30 + 2</gadget>
<output>32</output>

<gadget id="calculator">32 / (1/2)</gadget>
<output>64</output>

<gadget id="calculator">64 + 1</gadget>
<output>65</output>

<gadget id="calculator">65 / (1/2)</gadget>
<output>130</output>

<result>130</result>