
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 line $y= \frac {m}{2}x$ intersects the circle $x^{2}+y^{2}+mx+ny-4=0$ at points $M$ and $N$, and $M, N$ are symmetrical about the line $x+y=0$. Then the length of the chord $MN$ is _____ .

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