input: def fibonacci_seq(n: int) -> int: 
      """ Generate the nth Fibonacci number. The Fibonacci sequence is a series of numbers 
      where each number is the sum of the two preceding ones, usually starting with 0 and 1.
      >>> fibonacci_seq(0)
      0
      >>> fibonacci_seq(1)
      1
      >>> fibonacci_seq(6)
      8
      """
output:     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