Students play games in groups. There are at least 2 people in groups of 4 and 5. How many people are there at least?
同学们分组玩游戏，4人一组、5人一组都少2人，最少有几人？
<gadget id="calculator">4 * 5</gadget>
<output>20</output>

<gadget id="calculator">20 - 2</gadget>
<output>18</output>

<result>18</result>