Dad took Xiaoyong to travel on July 28th, and returned home on August 3rd. How many days did Xiaoyong and his father's trip last?
爸爸带着小勇7月28日开始旅游，8月3日回到家，小勇和爸爸的这趟旅游历时多少天．
<gadget id="calculator">31 - 28</gadget>
<output>3</output>

<gadget id="calculator">3 + 1 + 3</gadget>
<output>7</output>

<result>7</result>