from itertools import permutations

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

t, win = 0, 0
for a in permutations(A):
	for b in permutations(B):
		cnt = 0
		t += 1
		for ai, bi in zip(a, b):
			if bi < ai: cnt += 1
		if len(b)/2 < cnt: win += 1

print(win/t)