504.md

class Solution:
    def convertToBase7(self, num: int) -> str:
        
        if num == 0:
            return "0"
        
        else:
            as_base_7 = ""
            is_positive = num >= 0
            num = abs(num)            

            while num > 0:
                num, digit = divmod(num, 7)
                as_base_7 = str(digit) + as_base_7

            return as_base_7 if is_positive else "-" + as_base_7