
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 real number range, let $x=\left(\frac{\sqrt{(a-2)(|a|-1)}+\sqrt{(a-2)(1-|a|)}}{1+\frac{1}{1-a}}+\frac{5 a+1}{1-a}\right)^{1988}$. Determine the unit digit of $x$.

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