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

A = list(itertools.permutations(A))
B = list(itertools.permutations(B))

wa = 0
wb = 0
for a in A:
    pa, pb = 0, 0
    for b in B:
        for i in range(N):
            if a[i] > b[i]:
                pa += 1
            else:
                pb += 1
        if pa > pb:
            wa += 1
        else:
            wb += 1
        pa, pb = 0, 0

ret = wa / (wa+wb)
print(ret)