Problem 2: Monotone (100pts)

A number is said to have monotone digits if its digits have an non-decreasing order from left to right when written down. For example, 1234 and 24555 have monotone digits, while 22000130 and 2024 don't.

Now, please write a recursive function is_monotone, which takes as input a number n and returns whether n has monotone digits. Specifically, is_monotone returns True if n has monotone digits, and returns False if not.

def is_monotone(n):
    """Returns whether n has monotone digits.
    Implement using recursion!

    >>> is_monotone(22000130)
    False
    >>> is_monotone(1234)
    True
    >>> is_monotone(24555)
    True
    >>> # Do not use while/for loops!
    >>> from construct_check import check
    >>> # ban iteration
    >>> check(LAB_SOURCE_FILE, 'is_monotone', ['While', 'For'])
    True
    """
    "*** YOUR CODE HERE ***"