
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 following four propositions:
1. Two lines that do not have common points are parallel;
2. Two lines that are perpendicular to each other are intersecting lines;
3. Lines that are neither parallel nor intersecting are skew lines;
4. Two lines that are not in the same plane are skew lines.
Among these propositions, the correct ones are __________. (Fill in the sequence number)

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