import math
from itertools import permutations
from functools import reduce
length = int(input())
A = [int(n) for n in input().split(" ")]
B = [int(n) for n in input().split(" ")]
answer = 0
total = 0
for_win = int(math.floor(length / 2)) + 1
for a_comb in permutations(A, length):
    for b_comb in permutations(B, length):
        temp_win = 0
        total += 1
        # print(a_comb, b_comb, for_win, total, answer)
        for i in range(length):
            if a_comb[i] > b_comb[i]:
                temp_win += 1
            if temp_win >= for_win:
                answer += 1
                break
                
            
print(answer / total)