
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  $ \{ a_n \}_{n\equal{}1}$  as follows:  $ a_1 \equal{} 1989^{1989}; \ a_n, n > 1,$  is the sum of the digits of  $ a_{n\minus{}1}$ . What is the value of  $ a_5$ ?

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