from math import factorial

cnt = 0

def dfs(depth, N, p, mask):
    global cnt
    if depth == N:
        wc = 0
        for i, j in enumerate(p):
            if A[j] > B[i]:
                wc += 1

        if 2*wc > N:
            cnt += 1

        return

    for i in range(N):
        if not(mask & (1 << i)):
            p[depth] = i
            dfs(depth + 1, N, p, mask ^ (1 << i))

N = int(input())
A = [int(i) for i in input().split()]
B = [int(i) for i in input().split()]

p = [0] * N
dfs(0, N, p, 0)

ans = cnt / factorial(N)

print(ans)