
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 a sequence $\{a_n\}$, the first $m(m\geqslant 4)$ terms form an arithmetic sequence with a common difference of $2$. Starting from the $(m-1)$-th term, $a_{m-1}$, $a_{m}$, $a_{m+1}$, ... form a geometric sequence with a common ratio of $2$. If $a_{1}=-2$, then $m=$ ______, and the sum of the first $6$ terms of $\{a_n\}$, $S_{6}=$ ______.

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