
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 an isosceles triangle ABC, the base angles are \(a^{\circ}\) and \(b^{\circ}\) where \(a = b\) and \(a + b\) must sum to less than \(180^{\circ}\) due to a small circular arc subtended by the apex angle being exactly \(60^{\circ}\). Find the greatest possible value of \(a\) if both \(a\) and \(b\) are prime numbers.
A) 11
B) 43
C) 53
D) 59

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