import itertools
n = int(input())
a = map(int, input().split(' '))
b = map(int, input().split(' '))

x = 0
y = 0

A = list(itertools.permutations(a))
B = list(itertools.permutations(b))

for a in A:
    for b in B:
        win = 0
        lose = 0
        for i in range(n):
            if a[i] > b[i]:
                win+=1
            elif a[i] < b[i]:
                lose += 1
        if win > lose:
            x += 1
        y += 1

print(x/y)