
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
If the sum of the digits of a four-digit number \(X\) is subtracted from the number itself, the result is a natural number \(N = K^2\), where \(K\) is a natural number that leaves a remainder of 5 when divided by 20 and a remainder of 3 when divided by 21. Find the number \(N\).

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