
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
Given a function \( f(x) \) defined on \( \mathbf{R} \) that satisfies \( f(x+1) = f(-x) \), and \( f(x) \) is defined as:
\[
f(x) = \begin{cases} 
1, & -1 < x \leq 0, \\
-1, & 0 < x \leq 1,
\end{cases}
\]
then what is \( f(f(3.5)) \)?

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