"""
Author: Shayna Fu
Date: June 23, 2020


Return the sum of the numbers in the array, returning 0
for an empty array. Except the number 13 is very unlucky,
so it does not count and numbers that come immediately after
 a 13 also do not count.


sum13([1, 2, 2, 1]) → 6
sum13([1, 1]) → 2
sum13([1, 2, 2, 1, 13]) → 6

"""

SOLUTION:

def sum13(nums):
  if len(nums) == 0:
    return 0
    
  sum = 0
  
  if len(nums) > 0 and nums[0] != 13:
    sum = nums[0]
    
  for i in range (1,len(nums),1):
    if nums[i] != 13 and nums[i-1] != 13:
      sum = sum + nums[i]
  return sum
