
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 following conclusions: ① If $a+b \gt 0$ and $ab \gt 0$, then $a \gt 0$ and $b \gt 0$; ② If $\frac{a}{b}=-1$, then $a+b=0$; ③ If $a \lt b \lt c$, then $|a-b|+|b-c|=|a-c|$; ④ If $-1 \lt a \lt 0$, then $a^2 \gt a \gt a^3 \gt \frac{1}{a}$, the correct one is ______ (fill in the number).

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