How many two-digit numbers have digits whose sum is a perfect square?
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
How many two-digit numbers have digits whose sum is a perfect square?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
17
How many two-digit numbers have digits whose sum is a perfect square?
train