
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 function $f(x) = |x-a| + m|x+a|$.  
(I) When $m=a=-1$, find the solution set of the inequality $f(x) \geq x$;  
(II) When the inequality $f(x) \geq 2$ ($0 < m < 1$) always holds, the range of real number $a$ is $\{a|a \leq -3 \text{ or } a \geq 3\}$, find the set of real number $m$.

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