
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
Consider the set $A=\{x\mid x^2 + 2x - 3 < 0\}$ and the set $B=\{x\mid |x+a| < 1\}$.

(1) If $a=3$, find $A \cup B$;
(2) Let proposition $p$ be "$x \in A$" and proposition $q$ be "$x \in B$". If $p$ is a necessary but not sufficient condition for $q$, determine the range of the real number $a$.

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