import itertools
import math

def read_data():
    N = int(input())
    As = list(map(int, input().split()))
    Bs = list(map(int, input().split()))
    return N, As, Bs

def solve(N, As, Bs):
    n_win = 0
    for bs in itertools.permutations(Bs):
        if len([1 for a, b in zip(As, bs) if a > b]) > N // 2:
            n_win += 1
    return 1.0 * n_win / math.factorial(N)

N, As, Bs = read_data()
print(solve(N, As, Bs))