
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 $$f(x)= \frac {x}{1-|x|}$$, several conclusions are drawn as follows:  
① $f(x)$ is an odd function; ② The range of the function $f(x)$ is $\mathbb{R}$; ③ If $x_1 \neq x_2$, then $f(x_1) \neq f(x_2)$ must hold; ④ The function $g(x) = f(x) + x$ has three zeros. Among these conclusions, the correct ones are \_\_\_\_\_\_ . (Please fill in the serial numbers of all conclusions you think are correct)

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