input: def fibonacci_seq(n: int) -> int:
      """ Returns the nth element of the Fibonacci sequence. 
      The Fibonacci sequence is defined as:
              fibonacci_seq(0) = 0
              fibonacci_seq(1) = 1
              fibonacci_seq(n) = fibonacci_seq(n-1) + fibonacci_seq(n-2) for n > 1
      >>> fibonacci_seq(0)
      0
      >>> fibonacci_seq(1)
      1
      >>> fibonacci_seq(5)
      5
      """
output:     if n == 0:
          return 0
      elif n == 1:
          return 1
      else:
          return fibonacci_seq(n-1) + fibonacci_seq(n-2)