
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 geometric sequence $\{a_n\}$, the sum of its first $n$ terms is $S_n$, satisfying $S_2+a_1=0$ and $a_3=12$.  
(I) Find the general formula for the sequence $\{a_n\}$.  
(II) Determine whether there exists a positive integer $n$ such that $S_n > 2016$. If it exists, find the minimum value of such $n$; if not, explain why.

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