def fib_binet(n):
    """
    Constant time solution using Binet's Fibonacci Number Formula.
    In real-use, GOLDEN_RATIO should be moved outside of this function
    to avoid unneccesary re-computation.
    """
    GOLDEN_RATIO = (1 + 5**0.5) / 2
    return int((GOLDEN_RATIO**n - (-GOLDEN_RATIO)**(-n)) / (5**0.5))