from itertools import permutations


N = int(input())
A = list(map(int, input().split()))
B = list(map(int, input().split()))

total = 0
res = 0

for workA in permutations(range(N)):
    for workB in permutations(range(N)):
        A_win, B_win = 0, 0
        total += 1
        workA = list(workA)
        workB = list(workB)

        for i in range(N):
            if A[workA[i]] > B[workB[i]]:
                A_win += 1
            elif A[workA[i]] < B[workB[i]]:
                B_win += 1
        
        if A_win > B_win:
            res += 1

print(res / total)