class Solution:
    def maxSumOfSquares(self, num: int, sum: int) -> str:
        if sum > 9 * num:
            return ""

        count9, rest = divmod(sum, 9)
        digits = ["9"] * count9
        if rest:
            digits.append(str(rest))

        digits += ["0"] * (num - len(digits))
        return "".join(digits)