906. Super Palindromes

Let's say a positive integer is a superpalindrome if it is a palindrome, and it is also the square of a palindrome.

Now, given two positive integers L and R (represented as strings), return the number of superpalindromes in the inclusive range [L, R].

Example 1:

Input: L = "4", R = "1000"
Output: 4
Explanation: 4, 9, 121, and 484 are *superpalindromes*.
Note that 676 is not a *superpalindrome*: 26 * 26 = 676, but 26 is not a palindrome.

Note:

1. 1 <= len(L) <= 18
2. 1 <= len(R) <= 18
3. L and R are strings representing integers in the range [1, 10^18).
4. int(L) <= int(R)