# UUID: f9ffc765-c41c-4ab9-929f-7044b00339d2
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]])

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

while expensive <= cheapest:
    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

print(time)