\problemname{Carry Cam Failure}

\noindent
Clearly, with 25-digit input, it's impractical to simply try
all possible numbers.  But since only the least significant
digit of the input affects the least significant digit of the
output, and the least significant two digits affect the least
significant two digits, etc., we can generate possibilities
recursively, digit by digit, checking as many digits as we have.
This might look like it can blow up exponentially but a little
bit of testing will show that it easily runs in time.

A slightly more efficient solution is possible if you note that
carryless squaring of a reversed number is just the reversed
result of carryless squaring of that number.  This means that
you can perform your recursion from the most significant digit
to the least significant digit, simplifying the check for minimal
correct result.
