Xiaoming's house is on the 6th floor. He and his father started to play the game of "rock, scissors, and cloth" from the 4th floor to go upstairs. It is stipulated that the winner can go up 3 steps each time, and the loser has to go down one step. After playing 20 times, Dad and Xiao Ming both went up from the 4th floor to the 6th floor, so how many steps are there between the two floors?
小明家在6楼，他和爸爸从4楼开始玩"石头，剪刀，布"的游戏上楼，规定每次获胜者可以上3级台阶，输的人要下一级台阶．当玩了20次之后，爸爸和小明都从4楼上到了6楼，那么两层楼之间有多少级台阶？
<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">2 * 20</gadget>
<output>40</output>

<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<result>20</result>