from itertools import permutations

N = int(input())
A = list(map(int, input().split()))
B = list(map(int, input().split()))


def judge(xs, ys):
    win = 0
    for x, y in zip(xs, ys):
        if x > y:
            win += 1
        else:
            win -= 1

    return win > 0


games = 0
win = 0
for a in permutations(A):
    for b in permutations(B):
        games += 1
        if judge(a, b):
            win += 1

ans = win / games
print(ans)