from heapq import heappush, heappop

N = int(input())
P = list(map(int, input().split()))
Q = list(map(int, input().split()))

ps = [p/1000 for p in P]
qs = [q/100 for q in Q]

qu = []
for p, q in zip(ps, qs):
    heappush(qu, (-p*q, q))

ans = 0
for i in range(1, 10**6):
    p, q = heappop(qu)
    ans += -p * i
    heappush(qu, (p * (1-q), q))

print(ans)