from itertools import permutations
N = int(input())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
total, vic = 0, 0
for a in permutations(A):
    for b in permutations(B):
        total += 1
        cnt = 0
        for i in range(N):
            if a[i] > b[i]:
                cnt += 1
        if cnt > N // 2:
            vic += 1
print(vic / total)