
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 $\left\{a_{n}\right.$ is defined as: $a_{0} = 0$, $a_{1} = a_{2} = 1$, and $a_{n+1} = a_{n} + a_{n-1} (n \in \mathbf{N})$. Find the greatest common divisor of $a_{2002}$ and $a_{1998}$.

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