import itertools

def fact(n):
    if n <= 1:
        return 1
    return n * fact(n-1)

n = int(input())
a = list(map(int, input().split()))
b = list(map(int, input().split()))

ans = 0
for i in itertools.permutations(a):
    for j in itertools.permutations(b):
        wa, wb = 0, 0
        for k in range(n):
            if i[k] > j[k]:
                wa += 1
            else:
                wb += 1
                
        if wa > wb:
            ans += 1

print(ans / fact(n) ** 2)