
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
Among the following statements, the correct statement number is ______.  
① If $x \neq 0$, then $x + \frac{1}{x} \geq 2$; ② If $xy > 0$, then $\frac{y}{x} + \frac{x}{y} \geq 2$;  
③ If $\theta$ is an acute angle, then the minimum value of $\sin \theta + \frac{1}{\sin \theta}$ is 2; ④ If $x + y = 0$, then $2^x + 2^y \geq 2$.

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