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

import itertools
ap=itertools.permutations(a)
bp=itertools.permutations(b)

ans=0
for aa in ap:
  for bb in bp:
    temp=0
    for aii,bii in zip(aa,bb):
      if aii>bii:
        temp+=1
    if n/2<temp:
      ans+=1

import math
print(ans/math.factorial(n))