import sys
#sys.setrecursionlimit(n)
import heapq
import re
import bisect
import random
import math
import itertools
from collections import defaultdict, deque
from copy import deepcopy
from decimal import *

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

aa = list(itertools.permutations(a))
bb = list(itertools.permutations(b))

win_count = 0
pt_count = 0
for ta in aa:
  for tb in bb:
    pt_count += 1
    win = 0
    for i in range(n):
      if ta[i] > tb[i]:
        win += 1
      if win > (n / 2):
        win_count += 1
        break
print(win_count / pt_count)