input: def fibonacci(n):
      if n == 0:
          return 0
      elif n == 1:
          return 1
      else:
          return fibonacci(n-1) + fibonacci(n-2)
  
  print(fibonacci(10))
  """
  You are asked to write a program that calculates the Fibonacci number at a given position. Below is an example of how you can implement this.
  
  Example:
  for n = 10, the output should be 55.
  """
output:     a, b = 0, 1
      for _ in range(2, n + 1):
          a, b = b, a + b
      return b