def fib(n):
    negative = False
    
    # check if n is negative
    if n < 0:
        negative = True
        n = n * -1
        
    # base case: n is 0 or 1  
    if n <= 1:
        if negative: return -n
        return n 
        
    # iterative case    
    a, b = 0, 1
    for _ in range(n-1):
        a, b = b, a + b
        
    # return result    
    if negative: return -b
    return b

# driver code
print([fib(i) for i in range(10)])
print([fib(-i) for i in range(10)])