import heapq
import time

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

pq = []
for pi, qi in zip(p, q):
    heapq.heappush(pq, (-pi * qi, qi))

start = time.time()
k = 1
ans = 0
while time.time() - start < 1.95:
    pro, qq = heapq.heappop(pq)
    ans += -pro * k
    k += 1

    heapq.heappush(pq, (pro * (1 - qq), qq))

print(ans)