
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

A phone number \( d_{1} d_{2} d_{3}-d_{4} d_{5} d_{6} d_{7} \) is called "legal" if the number \( d_{1} d_{2} d_{3} \) is equal to \( d_{4} d_{5} d_{6} \) or to \( d_{5} d_{6} d_{7} \). For example, \( 234-2347 \) is a legal phone number. Assume each \( d_{i} \) can be any digit from 0 to 9. How many legal phone numbers exist?

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