def expo2(n: int):
	"""
	Returns the exponent of a power of two
	Using bit manipulation

	Parameters
	----------
	n : int

	Returns
	-------
	p : int,
		such as n = 2 ** p
	"""
	pow2 = (n & (n - 1) == 0)
	if not pow2:
		return "not a power of tow"
	return n.bit_length() - 1