The outstanding students of class 4 and class 1 took pictures, and they were divided into groups of 4 or 5. At least how many students are there in this group?
四1班的优秀学生进行照相，4人一组或5人一组都正好分完，这批学生至少有多少人？
<gadget id="calculator">4 * 5</gadget>
<output>20</output>

<result>20</result>