
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 natural number is divisible by 7 and is written with identical digits. How many digits can this number have? How many digits can the number have if it is written with identical digits and is divisible by a) 43, b) 41, c) 301, d) 3, e) 21?

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