def frac_knapsack(vl, wt, w, n):

    r = sorted(zip(vl, wt), key=lambda x: x[0] / x[1], reverse=True)
    vl, wt = [i[0] for i in r], [i[1] for i in r]
    acc = list(accumulate(wt))
    k = bisect(acc, w)
    return (
        0
        if k == 0
        else sum(vl[:k]) + (w - acc[k - 1]) * (vl[k]) / (wt[k])
        if k != n
        else sum(vl[:k])
    )