2023-07-21 16:40:56 +0300 MSK

class Solution:
    def addDigits(self, num: int) -> int:
        sum = 0
        while num > 0:
            sum += num % 10
            num //= 10
        
            if num == 0 and sum > 9:
                num, sum = sum, 0
                
        return sum