from itertools import permutations

N = int(input())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
win_A = 0
p = 0
for a in permutations(A, N):
    for b in permutations(B, N):
        p += 1
        x = y = 0
        for i in range(N):
            if b[i] < a[i]:
                x += 1
            else:
                y += 1
        if y < x:
            win_A += 1
print(win_A/p)