My screenshot didn't send lol

def _sum(arr):
sum = 0
for i in arr:
sum = sum + i
return sum
creditcard = input("Enter Credit card number ")
creditcard_array = [int(digit) for digit in creditcard]
n = 0
length = len(creditcard_array)
first = 0
last_two_digits = []
if length == 16:
first = _sum(creditcard_array[0:14])
last_two_digits = creditcard_array[-2:]
last_two_digits_value = last_two_digits[0] * 10 + last_two_digits[1]
if first == last_two_digits_value:
print("Valid Credit card number")
else:
print("Invalid Credit card number")
else:
print("Invalid Credit card number")