
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 sum of the first $n$ terms of the sequence $a_n$ is denoted as $S_n$. If $S_n - S_{n - 1} = 2n - 1$ for $n \geqslant 2$, and $S_2 = 3$, find the value of $a_1 + a_3$.

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