input: Write a function to calculate the average of a list of positive integers and output the result. The function should return the average value. If the list is empty, it should return 0.
  assert calculate_average_positive_integers([1, 5, 6, 7, 8])==5.4
  assert calculate_average_positive_integers([10, 20, 30, 40, 50])==30.0
  assert calculate_average_positive_integers([3, 6, 9, 12])==7.5
  assert calculate_average_positive_integers([])==0
  assert calculate_average_positive_integers([1])==1.0
output: def calculate_average_positive_integers(lst):
      if not lst:
          return 0
      return sum(lst) / len(lst)