
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
Let \( n \) denote the smallest positive integer that is divisible by both \( 5 \) and \( 9 \), and whose base-10 representation consists of only \( 5 \)'s and \( 9 \)'s, with at least one of each. What are the last four digits of \( n \)?
- **A)** 5555
- **B)** 5999
- **C)** 9595
- **D)** 9995
- **E)** 9959

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