
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 sequence $\{a\_n\}$ with the sum of its first $n$ terms denoted as $S\_n$. It is known that $S\_n^2 - 2S\_n - a\_nS\_n + 1 = 0$ for $n=1, 2, 3, ...$.

(1) Find $a\_1$ and $a\_2$.

(2) Find the expression for $S\_n$.

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