import itertools, math

n = int(input())
a = list(map(int, input().split()))
b = list(map(int, input().split()))

de = math.factorial(n)
nu = 0
for perm in itertools.permutations(range(n)):
    count = 0
    for i in range(n):
        if a[i] > b[perm[i]]:
            count += 1
        elif a[i] < b[perm[i]]:
            count -= 1
    if count > 0:
        nu += 1
print(nu / de)