Teacher Li took a batch of books and gave them to 36 students. Every time he came to a classmate’s home, Teacher Li gave half of all the books to him, and each student also returned a copy to her. In the end, Teacher Li still had 2 books left. Books, so how many books did Mr. Li take.
李老师拿着一批书送给36位同学，每到一位同学家里，李老师就将所有的书的一半给他，每位同学也都还她一本，最后李老师还剩下2本书，那么李教师原来拿了多少本书．
<gadget id="calculator">2 - 1</gadget>
<output>1</output>

<gadget id="calculator">1 * 2</gadget>
<output>2</output>

<gadget id="calculator">1 * 1 * 2</gadget>
<output>2</output>

<gadget id="calculator">1 * 1 * 1 * 2</gadget>
<output>2</output>

<gadget id="calculator">1 * 1 * 1 * 1 * 2</gadget>
<output>2</output>

<result>2</result>