#int(input())
#map(int, input().split())
#list(map(int, input().split()))

N = int(input())
A = list(map(int, input().split()))
B = list(map(int, input().split()))

ans = 0
x = 0


def time(x, a, b):
    return a / (1 + x) + b * (1 + x)

ans = 0

c = []
a = 0
b = 0

for i in range(N):
    a += A[i]
    b += B[i]
    c.append([max(1, (a/b)**0.5)-1, i+1])

c = sorted(c, reverse=True)

k = 0
u = [0] * N
while c:
    t = c.pop()
    if t[1] > k:
        sa = 0
        sb = 0
        for i in range(k, t[1]):
            sa += A[i]
            sb += B[i]
        for i in range(k, t[1]):
            u[i] = max(0, (sa/sb) ** 0.5 - 1)
        k = t[1]

for i in range(N):
    ans += time(u[i], A[i], B[i])

print(ans)