
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
In a certain sequence, the first term is $a_1=1001$ and the second term is $a_2=1002$. The values of the subsequent terms are chosen so that $a_n+a_{n+1}+a_{n+2}=n$ for all $n \geq 1$. Determine $a_{1000}$.

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