import sys
input = lambda : sys.stdin.readline().rstrip()

sys.setrecursionlimit(2*10**5+10)
write = lambda x: sys.stdout.write(x+"\n")
debug = lambda x: sys.stderr.write(x+"\n")
writef = lambda x: print("{:.12f}".format(x))


n = int(input())
p = list(map(int, input().split()))
q = list(map(int, input().split()))
p = [v/1000 for v in p]
q = [v/100 for v in q]
from heapq import heappop as hpp, heappush as hp, heappushpop as hppp, heapreplace as hr
from random import random as r
def sub():
    h = [(-v*q[i],i) for i,v in enumerate(p)]
    heapify(h)
    ans = 0
    count = [0]*n
    total = 1
    pp = 1
    for ii in range(10**6):
        pr,i = h[0]
        pr *= -1
        pr2 = (1-q[i])*pr
        hr(h, (-pr2, i))
        ans += (ii+1)*pr
#         print(ans, pr)
    return ans
ans = sub()
print(ans)