There are 100 seats in a row, at least how many seats are occupied so that the people behind must sit between two people.
一排有100个座位，至少有多少个座位有人坐，才能使后面的人必须坐在某两个人的中间．
<gadget id="calculator">50 + 1</gadget>
<output>51</output>

<result>51</result>