import itertools
import math
import numpy as np


N = int(input())

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

per1 = list(itertools.permutations(list(range(N)), N))
per2 = list(itertools.permutations(list(range(N)), N))
cnt = 0
count = 0
c = 0
for x in per1:
    for y in per2:
        aa = np.array([ a[l] for l in x])
        bb = np.array([ b[m] for m in y])

        if np.where(aa>bb, True, False).sum() > N/2:
            count += 1


ans = count / math.factorial(N) ** 2
print(ans)