input: Write a python function to find the median of a list of numbers.
  assert median([3, 4, 5, 9, 12, 15]) == 7.0
  assert median([1, 2, 3, 4, 5]) == 3
  assert median([10, 20, 30, 40, 50, 60]) == 35.0
output: def median(lst):
      sorted_lst = sorted(lst)
      n = len(sorted_lst)
      mid = n // 2
  
      if n % 2 == 0:
          return (sorted_lst[mid - 1] + sorted_lst[mid]) / 2.0
      else:
          return sorted_lst[mid]