from itertools import permutations
from math import factorial
n=int(input())
A=list(map(int,input().split()))
B=list(map(int,input().split()))
ans=0
for A_p in permutations(A,n):
  for B_p in permutations(B,n):
    cnt=0
    for i in range(n):
      if A_p[i]>B_p[i]:
        cnt+=1
    if cnt>n//2:
      ans+=1
print(ans/(factorial(n)**2))