
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
We define a number as a mountain number if its middle digits are larger than any other digits (for even digit numbers, consider the pair as the middle). For instance, 7397 and 4956 are mountain numbers. How many 4-digit mountain numbers are there?

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