# 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

def sum13(nums):
  sum = 0
  
  skipNext = False
  for i in nums:
    if i == 13:
      skipNext = True
      continue
    
    if skipNext == True:
      skipNext = False
      continue
      
    sum += i

  return sum