def resolve():
    import sys
    import itertools
    import math

    readline = sys.stdin.readline

    N = int(readline().strip())
    A = [int(x) for x in readline().split()]
    B = [int(x) for x in readline().split()]
    ans = 0

    for i in itertools.permutations(A):
        for j in itertools.permutations(B):
            win, lose = 0, 0
            for k in range(N):
                if i[k] > j[k]:
                    win += 1
                else:
                    lose += 1
            if win > lose:
                ans += 1
    print(ans / math.factorial(N) ** 2)


resolve()