A four-digit perfect square number is created by placing two positive two-digit perfect square numbers next to each other. What is the four-digit square number?
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
A four-digit perfect square number is created by placing two positive two-digit perfect square numbers next to each other. What is the four-digit square number?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
1681
A four-digit perfect square number is created by placing two positive two-digit perfect square numbers next to each other. What is the four-digit square number?
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