Deleting digits

def del_digits(n, count=0, last_digit=None):
    if n == 0:
        return count
    digits_str = str(n)
    digits = [int(d) for d in digits_str]

    for digit in sorted(set(digits), reverse=True):
        new_n = n - digit
        if new_n >= 0 and new_n < n:
            return del_digits(new_n, count + 1, digit)


    return count



if __name__ == "__main__":
    n = int(input())
    print(del_digits(n))

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 19, in <module>
    print(...

Test 8

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 19, in <module>
    print(...

Test 9

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 19, in <module>
    print(...

Test 10

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 19, in <module>
    print(...

Test 11

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 19, in <module>
    print(...

Test 12

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 19, in <module>
    print(...

Test 13

Verdict: RUNTIME ERROR

Traceback (most recent call last):
  File "input/code.py", line 19, in <module>
    print(...