Xiao Ming's father goes to the gym every 4 days, and Xiao Ming's mother goes to the gym every 5 days. On June 4, both parents go to the gym at the same time. When will they go to the gym at the same time next time?
小明的爸爸每4天去一次健身房，小明的妈妈每5天去一次健身房，6月4日，爸爸妈妈同时去健身房，下次他们再同时到健身房的时间是6月多少日．
<gadget id="calculator">4 * 5</gadget>
<output>20</output>

<gadget id="calculator">4 + 20</gadget>
<output>24</output>

<result>24</result>