The escalator goes from bottom to top, Xiao Ming walks 36 steps from top to bottom, Xiao Hong walks from bottom to top 20 steps to the top, it is known that Xiao Ming's speed is twice that of Xiao Hong, how many steps are there from bottom to top?
自动扶梯由下向上，小明由上向下走了36级到底，小红由下向上走了20级到顶，已知小明速度是小红的两倍，问由底到顶共几级？
<gadget id="calculator">36 + 20</gadget>
<output>56</output>

<gadget id="calculator">56 / 2</gadget>
<output>28</output>

<result>28</result>