import math
import itertools
n = int(input())
a = list(itertools.permutations(list(map(int,input().split()))))
b = list(itertools.permutations(list(map(int,input().split()))))
won = 0
lost = 0
for i in range(math.factorial(n)):
    for j in range(math.factorial(n)):
        win = 0
        lose = 0
        for x in zip(a[i],b[j]):
            if x[0] > x[1]:win +=1
            if x[0] <= x[1]:lose += 1
        if win > lose:
            won += 1
        else:lost += 1
print(won/(won+lost))