
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 hyperbola $C:\frac{y^2}{a^2}-\frac{x^2}{b^2}=1 (a>0, b>0)$ has its upper focus at $F$, and points $A$ and $B$ are on the curve. If quadrilateral $OFAB$ is a rhombus, then the eccentricity of $C$ is ____.

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