
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
In the Cartesian coordinate plane $(xOy)$, if line $l_{1}: \begin{cases}x=2s+1 \\ y=s\end{cases}(s\text{ is a parameter})$ and line $l_{2}: \begin{cases}x=at \\ y=2t-1\end{cases}(t\text{ is a parameter})$ are parallel, the value of the constant $a$ is $\_\_\_\_\_\_$.

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