
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 $A_n^5 = 56 C_n^7$ and $(1-2x)^n = a_0 + a_1x + a_2x^2 + a_3x^3 + \dots + a_nx^n$.
(I) Find the value of $n$;
(II) Find the value of $a_1 + a_2 + a_3 + \dots + a_n$.

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