def run():
  N = int(input())
  A_list = list(map(int, input().split()))
  B_list = list(map(int, input().split()))
  array_A_list = array(A_list, N)
  array_B_list = array(B_list, N)
  #print(array_A_list)
  num_win = 0
  total = 0
  for a_list in array_A_list:
    for b_list in array_B_list:
      sub_total = 0
      total += 1
      #print(a_list, b_list)
      for a, b in zip(a_list, b_list):
        if a > b: sub_total += 1
      if sub_total > N//2:
        num_win += 1
  print(num_win/total)
  #print(num_win, total)

def add(pre_list, n_list):
  new_list = []
  for pre in pre_list:
    for n in n_list:
      if (n in pre) == False:
        new_list.append(pre+[n])
  return new_list

def array(n_list, N):
  res_list = [[n] for n in n_list]
  for n in range(N-1):
    res_list = add(res_list, n_list)
  return res_list
  
if __name__ == '__main__':
  run()