
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 palindrome is a positive integer that reads the same backward as forward, such as 22, 11, 3443, 94249, etc. It is clear that there are 9 two-digit palindromes: 11, 22, 33, ..., 99. There are 90 three-digit palindromes: 101, 111, 121, ..., 191, 202, ..., 999. Then:
(I) How many four-digit palindromes are there?
(II) How many palindromes are there with $2n+1$ ($n\in\mathbb{N}^+$) digits?

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