from collections import defaultdict, deque
from bisect import bisect_right, bisect_left
from random import randint
from itertools import permutations
# from more_itertools import distinct_permutations
from heapq import heappush, heappop
import sys
import math
import copy
# from sortedcontainers import SortedList


sys.setrecursionlimit(100000000)

n = int(input())
a = list(map(int, input().split()))
b = list(map(int, input().split()))

ans = 0
cnt2 = 0
for p1 in permutations(a):
    for p2 in permutations(b):
        cnt2 += 1
        cnt = 0
        for i in range(n):
            if p1[i] > p2[i]:
                cnt += 1
        if cnt > (n - cnt):
            ans += 1
ans /= cnt2
print(ans)