参考代码：

import math


class Solution:
    def checkSum(self, num):
        if num < 0:
            return False
        for i in reversed(range(0, int(math.sqrt(num)) + 1)):
            if i * i == num:
                return True
            j = num - i * i
            k = int(math.sqrt(j))
            if k * k == j:
                return True
        return False