There are 5 steps in front of the post office. It is stipulated that one step can only go up one or two steps. Ask how many ways to go up to the top.
邮局门前有5个台阶，规定：一步只能上一级或两级，问上到上面，共有多少种方法．
<gadget id="calculator">1 + 2 + 2 + 1 + 2</gadget>
<output>8</output>

<result>8</result>