There are 6 steps, and Xiao Ming walks from bottom to top. If he can only cross one or two steps at a time, how many different ways can he walk?
有6级台阶，小明从下向上走，若每次只能跨过一级或两级，他有多少种不同走法．
<gadget id="calculator">5 ** 1</gadget>
<output>5</output>

<gadget id="calculator">1 + 5 + 6 + 1</gadget>
<output>13</output>

<result>13</result>