
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
Define the sequence $\left\{a_{n}\right\}_{n=1}^{\infty}$ as follows: $a_{1}=1989^{1989}$, and for $n>1$, $a_{n}$ is equal to the sum of the digits of $a_{n-1}$. What is $a_{5}$?

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