from itertools import permutations
import math
N = int(input())
A = list(map(int,input().split()))
B = list(map(int,input().split()))
win = 0
for x in permutations(B,N):
    cnt = 0
    for i in range(N):
        if A[i]>x[i]:
            cnt += 1
    if cnt>N-cnt:
        win += 1
print(win/math.factorial(N))