
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
Let X, Y, Z be different lines or planes in space. Among the following four situations, for which ones does the statement "If X is perpendicular to Z and Y is perpendicular to Z, then X is parallel to Y" hold true? (Fill in the serial number)  
① X, Y, Z are lines; ② X, Y are lines, Z is a plane; ③ Z is a line, X, Y are planes; ④ X, Y, Z are planes.

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