
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
Given the sequence 2008, 2009, 1, -2008, -2009, ..., where each term from the second term onward is equal to the sum of the term before it and the term after it, calculate the sum of the first 2013 terms of this sequence.

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