
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 distinct lines $l$, $m$, $n$ and planes $\alpha$, $\beta$, $\gamma$ be given, and consider the following three propositions:  
① If $l$ and $m$ are skew lines, $l \subset \alpha$, $m \subset \beta$, then $\alpha \parallel \beta$  
② If $\alpha \parallel \beta$, $l \subset \alpha$, $m \subset \beta$, then $l \parallel m$;  
③ If $\alpha \cap \beta = l$, $\beta \cap \gamma = m$, $\gamma \cap \alpha = n$, and $l \parallel \gamma$, then $m \parallel n$.  
The number of true propositions is     .

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