import itertools

n = int(input())

A = list(map(int, input().split()))
B = list(map(int, input().split()))
game_count = 0
game_A = 0

for cards_a in list(itertools.permutations(A, n)):
    for cards_b in list(itertools.permutations(B, n)):
        win_a = 0
        win_b = 0
        for card_a, card_b in zip(cards_a, cards_b):
            if card_a > card_b:
                win_a += 1
            elif card_b > card_a:
                win_b += 1

        game_count += 1
        if win_a > win_b:
            game_A += 1

print(game_A/game_count)