
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
The general term formula of the sequence {a<sub>n</sub>} is a<sub>n</sub>\=n(sin $$\frac {nπ}{2}$$+cos $$\frac {nπ}{2}$$), and its sum of the first n terms is S<sub>n</sub>. Find S<sub>2019</sub>.

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