input: Write a function to calculate the sum of all elements in a list that are divisible by 3. If the given list is empty then return 0.
  assert divisibleBy3([4, 6, 17, 24, 5, 9])==39
  assert divisibleBy3([3, 5, 7, 11])==3
  assert divisibleBy3([])==0
  assert divisibleBy3([2, 4, 8])==0
output: def divisibleBy3(lst):
      return sum(x for x in lst if x % 3 == 0)