
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
Calculate the sum of the series $1 - 2 - 3 + 4 + 5 - 6 - 7 + 8 + 9 \cdots + 1995 + 1996 - 1997 - 1998 + 1999 + 2000$.

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