import itertools
import math

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

count = 0
total = 0
for b in itertools.permutations(B):
    wins = 0
    for i in range(N):
        wins += 1 if b[i] < A[i] else 0
    if wins > N//2:
        count += 1

fact = math.factorial(N)
print(float(count / fact))