#yukicoder No133
import itertools

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


Comb = list(itertools.permutations(B))
ans_all = len(Comb)
ans_win = 0
for i in range(ans_all):
 B_ = list(Comb[i])
 a_win = 0
 b_win = 0
 for j  in range(len(B_)):
  if(A[j] > B_[j]): a_win += 1
  elif(A[j] < B_[j]): b_win += 1
 if(a_win > b_win): ans_win += 1

ans = ans_win/ans_all
print(ans)