def factorial(n):
    """Recursive calculation of n!"""
    if n <= 1: # Base Case
        return 1
    return n * factorial(n - 1) # Recursive Step

def fibonacci(n):
    """Recursive Fibonacci - O(2^n) complexity"""
    if n <= 1:
        return n
    return fibonacci(n - 1) + fibonacci(n - 2)