from itertools import permutations

n = int(input())
A, B = [[int(x) for x in input().split()] for i in range(2)]
win = 0
cnt = 0


def fight(a: tuple, b: tuple) -> None:
    global win, cnt
    mini_win = 0
    cnt += 1
    for i in range(n):
        if a[i] > b[i]:
            mini_win += 1
        else:
            mini_win -= 1
    if mini_win > 0:
        win += 1


def main() -> None:
    for Ai in permutations(A):
        for Bi in permutations(B):
            fight(Ai, Bi)

    print("{:.2}".format(win / cnt))


if __name__ == "__main__":
    main()