import itertools

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

a_perms = list(itertools.permutations(a))
b_perms = list(itertools.permutations(b))

count = 0
total = len(a_perms) * len(b_perms)

for a_p in a_perms:
    for b_p in b_perms:
        a_win = 0
        for i in range(n):
            if a_p[i] > b_p[i]:
                a_win += 1
        if a_win > n // 2:
            count += 1

probability = count / total
print("{0:.6f}".format(probability))