
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 line $l_1$: $(a+3)x+y-3=0$ and the line $l_2$: $5x+(a-3)y+4=0$, if the direction vector of $l_1$ is the normal vector of $l_2$, then the real number $a= \boxed{-2}$.

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