
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 sets $M = \{x | x(x-a-1) < 0, x \in \mathbb{R}\}$, $N = \{x | x^2 - 2x - 3 \leq 0\}$, if $M \cup N = N$, find the range of the real number $a$.

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