
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
Let \( n \geq 1 \) be an integer. We have \( n \) cubes with side lengths \( 1, 2, \ldots, n \). We want to stack them in a certain order such that a cube with side length \( k \) can only be placed on top of a cube with side length \( l \) where \( l \geq k-2 \). How many different such stackings are there?

Present the answer in LaTex format: \boxed{Your answer}
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