
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
Calculate the total number of 4-digit mountain numbers. A 4-digit mountain number is defined such that the middle two digits are larger than the first and the last digit, and the first and last digits are not the same.

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