from itertools import permutations
N = int(input())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
def factorial(n):
    if n == 0:
        return 1
    else:
        return n*factorial(n-1)
Awin = 0
for a in permutations(range(N),N):
    for b in permutations(range(N),N):
        akachi = 0
        bkachi = 0
        for i in range(N):
            if A[a[i]] > B[b[i]]:
                akachi += 1
            elif A[a[i]] < B[b[i]]:
                bkachi += 1
        if akachi > bkachi:
            Awin += 1
print(Awin/(factorial(N)**2))