
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
The relationship between two parallel lines and a circle is defined as follows: If two parallel lines and a circle have four different common points, then the two parallel lines and the circle are said to "intersect"; if two parallel lines and a circle have no common points, then the two parallel lines and the circle are said to "be separate"; if two parallel lines and a circle have one, two, or three different common points, then the two parallel lines and the circle are said to "be tangent". Given the line $l_{1}:2x-y+a=0$, $l_{2}:2x-y+a^{2}+1=0$ and the circle $x^{2}+y^{2}+2x-4=0$ are tangent, then the range of values for $a$ is __________.

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