input: Write a function to generate the Fibonacci number at a given position. If the position is 0 or 1, return the position itself. For other positions, return the sum of the two preceding Fibonacci numbers.
  def fibonacci(n):
      if n == 0:
          return 0
      elif n == 1:
          return 1
      else:
          return fibonacci(n-1) + fibonacci(n-2)
  
  n = 10
  print(fibonacci(n))
  assert fibonacci(10) == 55
  assert fibonacci(5) == 5
  assert fibonacci(0) == 0
  assert fibonacci(1) == 1
  assert fibonacci(7) == 13
output: def fibonacci(n):
      if n == 0:
          return 0
      elif n == 1:
          return 1
      else:
          return fibonacci(n-1) + fibonacci(n-2)