from itertools import permutations

n = int(input())
a = list(map(int, input().split()))
b = list(map(int, input().split()))
p = list(permutations(a))
m = len(p)
win = 0
for i in range(m):
    cnt = 0
    for j in range(n):
        if p[i][j] > b[j]:
            cnt += 1
    if cnt > n / 2:
        win += 1
print(win / m)