The school held a parent-teacher meeting. There were 496 parents from the first grade and 365 parents from the second grade. The school has prepared 900 seats for the parents. How many vacant seats are there?
学校开家长会，一年级来了496名家长，二年级来了365名家长，学校为家长们准备了900个座位，请问还有多少个空座位？
<gadget id="calculator">900 - 496 - 365</gadget>
<output>39</output>

<result>39</result>