Simplify the following expression: $\sqrt{28 + \sqrt{1296}}$
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Simplify the following expression: $\sqrt{28 + \sqrt{1296}}$
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
8
Simplify the following expression: $\sqrt{28 + \sqrt{1296}}$
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