# UUID: 3f80e7ce-5ce9-4c0f-af0b-bf06e01f606f
N = int(input())
exp = [int(x) for x in input().split()]
mat = [int(x) for x in input().split()]

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

for i in range(N):
    whole[i]=[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)