
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 system $(xOy)$, if line $l$: $\begin{cases} x=t, \\ y=t-a, \end{cases}(t\text{ is a parameter})$ passes through the right vertex of ellipse $C$: $\begin{cases} x=3\cos φ, \\ y=2\sin φ \end{cases}(φ\text{ is a parameter})$, then the value of constant $a$ is _______.

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