from itertools import permutations

N = int(input())

A = list(map(int, input().split()))
B = list(map(int, input().split()))

perm = permutations(A, N)

ans = [0, 0]

for a in perm:
  cnt = [0, 0]
  for i in range(N):
    if a[i] > B[i]:
      cnt[0] += 1
    else:
      cnt[1] += 1
  if cnt[0] > cnt[1]:
    ans[0] += 1
  else:
    ans[1] += 1

print(ans[0] / sum(ans))