def main():
    N = int(input())
    exp = list(map(int, input().split()))
    mat = list(map(int, input().split()))

    time = 0
    whole = []
    experience = 0
    cheapest = N - 1
    expensive = 0

    for i in range(0, N):
        whole.append([mat[i], exp[i]])

    all1 = sum(mat)
    whole.sort(key=lambda x: -x[1])

    while all1 != experience:
        if whole[cheapest][1] <= experience:
            time += whole[cheapest][0]
            experience += whole[cheapest][0]
            cheapest -= 1
        else:
            minimum = min(whole[expensive][0], whole[cheapest][1] - experience)
            time += minimum * 2
            experience += minimum
            whole[expensive][0] -= minimum
            if whole[expensive][0] == 0:
                expensive += 1

    return time


print(main())