input: ### Instruction:
  Generate a Python program to calculate the Fibonacci number at a given position.
  
  Write a function to calculate the Fibonacci number at a given position. The function should return the Fibonacci number for the specified position. If the position is 0, return 0. If the position is 1, return 1. For any other position, return the sum of the two preceding Fibonacci numbers.
  
  assert fibonacci(0)==0
  assert fibonacci(1)==1
  assert fibonacci(2)==1
  assert fibonacci(5)==5
  assert fibonacci(10)==55
output:     
  def fibonacci(n: int) -> int:
      if n == 0:
          return 0
      elif n == 1:
          return 1
      else:
          a, b = 0, 1
          for _ in range(2, n + 1):
              a, b = b, a + b
          return b
  