Mr. Li does housework at home, uses the washing machine to wash clothes for 20 minutes, mops the floor for 12 minutes, hangs clothes for 3 minutes and boils water for 5 minutes. How long does it take at least to finish these chores?
李老师在家做家务用洗衣机洗衣服20分钟，拖地板12分钟，晾衣服3分钟烧水5分钟，做完这些家务至少要多少分钟．
<gadget id="calculator">20 + 3</gadget>
<output>23</output>

<result>23</result>