import sys
input=lambda: sys.stdin.readline().rstrip()
n=int(input())
A=[int(i) for i in input().split()]
B=[int(i) for i in input().split()]
ct=0
import itertools
for p in itertools.permutations(range(n)):
  win=0
  for i in range(n):
    if A[i]>B[p[i]]:
      win+=1
  if 2*win>n:
    ct+=1
for i in range(n):
  ct/=(i+1)
print(ct)