import itertools
import numpy as np

N = int(input())
cards_a = list(map(int, input().split()))
cards_b = list(map(int, input().split()))

total = 0
win_a = 0
for pattern_a in itertools.permutations(cards_a):
    for pattern_b in itertools.permutations(cards_b):
        pattern_a = np.array(list(pattern_a))
        pattern_b = np.array(list(pattern_b))
        fight = np.sum(pattern_a > pattern_b)
        if fight > N - fight:
            win_a += 1
        total += 1

print(win_a / total)