
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 propositions:
1. If $m \parallel n$, $m \perp \alpha$, then $n \perp \alpha$.
2. If $m \perp \alpha$, $n \perp \alpha$, then $m \parallel n$.
3. If $m \perp \alpha$, $m \perp n$, then $n \parallel \alpha$.
4. If $m \parallel \alpha$, $m \perp n$, then $n \perp \alpha$.

The sequence number of the correct proposition is $\boxed{\text{answer}}$.

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