STEP 1, STEP2

Liam's house has a staircase with 12 steps. He can go down the steps one at a time or two at time.
In how many different ways can Liam go down the 12 steps, taking one or two steps at a time?

For example: He could go down 1 step, then one step, then 2 steps, then 2, 2, 1, 1, 1, 1.