
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
Consider the function $f(x)=x\sin |x| + \ln \frac{2019-x}{2019+x}$, where $x \in [-2018,2018]$. If the range of this function is $(m,n)$, find the value of $f(m+n)$.

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