Computes the LCS-based F-measure score
    Source: http://research.microsoft.com/en-us/um/people/cyl/download/papers/
    rouge-working-note-v1.3.1.pdf

    :param llcs: Length of LCS
    :param m: number of words in reference summary
    :param n: number of words in candidate summary
    :returns float: LCS-based F-measure score

def _f_lcs(llcs, m, n):
    """
    Computes the LCS-based F-measure score
    Source: http://research.microsoft.com/en-us/um/people/cyl/download/papers/
    rouge-working-note-v1.3.1.pdf

    :param llcs: Length of LCS
    :param m: number of words in reference summary
    :param n: number of words in candidate summary
    :returns float: LCS-based F-measure score
    """
    r_lcs = llcs / m
    p_lcs = llcs / n
    beta = p_lcs / r_lcs
    num = (1 + (beta ** 2)) * r_lcs * p_lcs
    denom = r_lcs + ((beta ** 2) * p_lcs)
    return num / denom