Python, how to do this question converting num to str? (no lists)

Complete the function below which takes in an integer number named "num" and returns True iff every third number (starting from index 0) in the given number is divisible by 3. So, we would want the number at index 0, and then the one at index 3, and then at index 6 and so on to all be multiples of 3. def check_every_third (num) (int) -> bool Return True iff every third number in the given number num is divisible by 3. >>> check-every-third(123456) False >check every third (3123456) True >> check every third (333333) True