import heapq, time

n = int(input())
p = list(map(int, input().split()))
q = list(map(int, input().split()))

pq = []
for i in range(n):
    heapq.heappush(pq, (-p[i] * q[i] / 100000, i))

start = time.time()
ans, cnt = 0, 1
while time.time() - start < 1.9:
    pp, id = heapq.heappop(pq)
    ans += -cnt * pp
    cnt += 1
    heapq.heappush(pq, (pp * (1 - q[id] / 100), id))

print(ans)