There are two groups of people who want to sit in a row of 120 seats. After the first group of people sit down, it happens that the second group of people must be in the seats adjacent to the first group of people. How many people are there in the first batch of seats?
有两批人要坐到排成一排的120个座位上，第一批人坐下后，恰好使得第二批入座的人必定在与第一批入座的人相邻的座位上．第一批入座的人至少有多少人．
<gadget id="calculator">120 / 3</gadget>
<output>40</output>

<result>40</result>