from heapq import heappop, heappush

n = int(input())
p_ls = map(lambda p: int(p) / 1000, input().split())
q_ls = map(lambda q: int(q) / 100, input().split())

hq = []
for p, q in zip(p_ls, q_ls):
    heappush(hq, (-p * q, 1 - q))

ans = 0
for i in range(1, 1000000):
    t, tq = heappop(hq)
    ans += -i * t
    heappush(hq, (t * tq, tq))

print(ans)