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))

total_cases = len(a_perms) * len(b_perms)
win_cases = 0

for a_seq in a_perms:
    for b_seq in b_perms:
        a_wins = 0
        for i in range(n):
            if a_seq[i] > b_seq[i]:
                a_wins += 1
        if a_wins > n - a_wins:
            win_cases += 1

probability = win_cases / total_cases
print("{0:.6f}".format(probability))