func_code: def fibonacci(n, first_number=0, second_number=1, counter=0):
      if n == 0:
          return 0
      elif n == 1:
          return 1
      elif n == counter:
          return second_number
      else:
          holder = second_number
          second_number += first_number
          first_number = holder
          return fibonacci(n, first_number, second_number, counter + 1)