from itertools import permutations

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

win = 0
cnt = 0
for pa in permutations(range(N)):
    for pb in permutations(range(N)):
        cnt += 1
        aw = 0
        bw = 0
        for a, b in zip(pa, pb):
            if A[a] > B[b]:
                aw += 1
            elif A[a] < B[b]:
                bw += 1
        if aw > bw:
            win += 1

ans = win / cnt
print(ans)