There are three different books on the shelf: "Scientific Public", "Colorful Literature" and "Mathematics Paradise". If you borrow at least one book and at most three books, how many different ways are there in total?
书架上有《科学大众》，《七彩文学》和《数学乐园》三本不同的书，如果最少借1本，最多借3本，一共有多少种不同的借法．
<gadget id="calculator">3 + 6 + 10</gadget>
<output>19</output>

<result>19</result>