import itertools
import math

N = int(input())
A = list(map(int,input().split()))
B = list(map(int,input().split()))
win = 0

for v in itertools.permutations(A, N):
    check = 0
    for n in range(N):
        if v[n] < B[n]:
            check += 1
    if check < N/2:
        win += 1
print(win/math.factorial(N))