
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
The sequence $\{ a_{n} \}$ is an arithmetic sequence with the sum of its first $n$ terms denoted as $S_{n}$. It is known that $S_{1}$, $S_{3}$, and $S_{2}$ form an arithmetic sequence.

(1) Find the common ratio $q$ of the sequence $\{ a_{n} \}$.

(2) If $a_{1} - a_{3} = 3$, find the sum $S_{n}$.

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