def fib (n: int) -> int:
	""" Returns the n'th Fibonacci number. 
	Note that this function uses zero style indexing, meaning that the first Fibonacci number has an index
	of zero (n=0)."""
	f_p, f_c= 0, 1
	for i in range(n):
		f_n = f_c + f_p
		f_p = f_c
		f_c = f_n
	return f_c