
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 student is rearranging all his stamps into a new album. If he pastes 20 stamps per page, the album will be insufficient. If he pastes 23 stamps per page, at least one page will remain empty. If he receives an additional identical album, each page containing 21 stamps, he will have a total of 500 stamps. How many pages are in the album?

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