def S(Lt, l):
    """
    Calculates the S coefficient
    Parameters
    ----------
    Lt : float
        The length way of liquid, [m]
    l : float
        The length way of liquid of one slot mix, [m]
    Returns
    -------
    Lt : float
        The S coefficient, [dismensionless]
    References
    ----------
    &&&&
    """     
    return Lt / l