def freq_to_channel(freq):
    """
	freq -- frequqncy in Hz
	return -- channel number
	"""
    if 2412000000 <= freq <= 2472000000:
        return 1 + int((freq - 2412000000) / (5 * 1000000))
    if freq == 2484000000:
        return 14
    if 5035000000 <= freq <= 5825000000:
        return 7 + int((freq - 5035000000) / (5 * 1000000))
    return None
