import itertools as it
import math

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

ans = 0
for pa in it.permutations(a, n):
  for pb in it.permutations(b, n):
    cnt = 0
    for i in range(n):
      if pa[i] > pb[i]:
        cnt += 1

    if cnt > n // 2:
      ans += 1

ans /= (math.factorial(n) ** 2)
print(ans)