
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
The natural number \( A \) has the following property: the number \( 1 + 2 + \cdots + A \) can be written (in base 10) as the number \( A \) followed by three other digits. Find \( A \).

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