
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 ellipse $C$: $\frac{x^{2}}{a^{2}}+ \frac{y^{2}}{b^{2}}=1(a > b > 0)$ with a focal length of $4$, and the point $(2,- \sqrt{2})$ lies on $C$.

(1) Find the equation of the ellipse $C$;

(2) If the line $y=x+m$ intersects the ellipse $C$ at two distinct points $A$ and $B$, and the midpoint $M$ of the segment $AB$ lies on the circle $x^{2}+y^{2}=1$, find the value of $m$.

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