
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 the sequence $\left\{a_{n}\right\}$ that satisfies
$$
a_{n-1} = a_{n} + a_{n-2} \quad (n \geqslant 3),
$$

let $S_{n}$ be the sum of the first $n$ terms. If $S_{2018} = 2017$ and $S_{2019} = 2018$, then find $S_{20200}$.

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