
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
If a three-digit number's tens digit is greater than both its units digit and hundreds digit, then this number is called an "umbrella number." From the six digits 1, 2, 3, 4, 5, 6, determine the number of three-digit numbers without repetition that can be formed using these digits.

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