I also solved in python, however, my code to pre-generate all "fair and square" numbers in the range 1->10^100 only took 6s to run. Didn't even need optimizatio

I also solved in python, however, my code to pre-generate all "fair and square" numbers in the range 1->10^100 only took 6s to run. Didn't even need optimization. I simply constructed the numbers outright, ie, there was no iteration in my code and trying to see if something fit. I just figured out a rule that would generate all those palindromes with no checking. I think that was what they were looking for in that submission. If anyone is curious, the rule is as follows. Any palindrome where the sum of the squares of the digits add up to strictly less than 10(9 or less) will be the square root of a "fair and square number". From there, I constructed them using a recursive method which finds the first half of numbers fitting that description and mirrors them to get the palindrome. I ended up getting an incorrect solution on C-large-2 but that was because I failed to realize that I would lose precision when finding the square roots of the bounds of the range. While integers in python can grow indefinitely math.sqrt() will give you a 32bit floating point number which will represent square roots of 10^14 numbers accurately but not square roots of 10^100 numbers. The diff which turns my program into one that gives correct answers has literally 3 changes lines(to use decimal.Decimal instead of the math library for doing square roots).