N = int(input())
l = [i for i in range(N)]
A = list(map(int, input().split()))
B = list(map(int, input().split()))

from itertools import permutations
ans = 0
facn = 1
for i in range(N):
    facn *= i + 1
for pA in permutations(l):
    for pB in permutations(l):
        cntA = 0
        cntB = 0
        for i, j in zip(pA, pB):
            if A[i] > B[j]:
                cntA += 1
            if A[i] < B[j]:
                cntB += 1
        if cntA > cntB:
            ans += 1 / facn ** 2
print(ans)