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