A palindrome number is a positive integer that reads the same forward and backward. For example, $1221$ and $8$ are palindrome numbers whereas $69$ and $157$ are not.  $A$ and $B$ are $4$-digit palindrome numbers.  $C$ is a $3$-digit palindrome number.  Given that $A-B=C$, what is the value of $C$?

Let's think step by step and output the final answer within \boxed{}.
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